Preface:
The author, Mark Humphreville is a Distinguished High Power shooter of many years who won the 1000yd. Wimbleton Match at Camp Perry a few years back shooting a pre-war M70 Winchester in 30-06 when most other competitors were using 300WM in actions of much more recent vintage. I had the pleasure of shooting with Mark on many occasions at Ft. Jackson and Ft. Gordon as well as Camp Perry. Mark lost the vision in his right eye in an accident many years ago and consequenty shoots the M70 left handed. To watch him shoot the rapid fire stages lefty with a right handed bolt gun is impressive. He is also a walking encyclopedia of small arms information as you shall see in the following text. The following article is a little lengthy, but worthy of your time for your small arms edification.
IT DON’T GO BANG-FIRES, HANGFIRES, MISFIRES AND SHORT ORDER
COOKS IN JERSEY
By Mark Humphreville
In looking over all the information I can find on the internet about “why it doesn’t go
bang” I notice that there is virtually no information for the average shooter to obtain the
knowledge needed to investigate these problems and possibly to correct the causes. I
hope to address that void with this article.
Background. While with the Army Small Caliber Lab and at Aberdeen Proving Ground
(APG) as Test Director Small Arms and Ammunition I was trained by some of the finest
minds in the business. They ranged from Primer Engineers that did nothing but play
with primers, mixes, etc their entire careers to Weapons and Ammunition Testing
Engineers at APG. What these folks taught me about small arms ignition reliability and
why they might or might not go bang was amazing to learn, and chances are I would have
never learned it anywhere else.
It must be understood, I grew up on the range so to speak. My father was a shooter, I
went to Camp Perry in l957 for first time and started loading ammo that same year. By
the time I finished high school, I had gone through over 25,000 primers. Like eveyone
else that shoots lots of ammo, has shot all his life and reads all that can be found, I felt I
had a pretty good basis of knowledge of what goes on in the gun business. I was
extremely lucky in having a great friend by the name of Larry Moore (Larry wrote many
articles for the shooter over his years) and he was chairman of the Configuration Control
Board at Rock Island Arsenal (RIA). He made the recommendation to the Army Small
Cal Weapons Lab that I be brought on board.
Upon arrival at the Army Small Cal. Lab, I learned in the first week that 20 years of
competitive experience was fun but did absolutely nothing to furthur my education in the
weapons field. When I went the the Small Cal Lab I was fortunate to make friends with
another bachelor who at that time had been in the ordnance field for 28 years; this guy
was an absolute walking computer filled with knowledge that he could bring up at the
mere mention of any ordnance subject. He talked incessantly and I listened intently. We
talked ordnance from the time we got in the car for the 37mile drive to work, all day at
work and on the way back to the big house we shared in Milford, Pa. At night we loaded
and on the weekends we went to the range. I worked side by side with him for over a
year and then got asked to come to the Special Projects Group working on the Dover
Devil Machinegun. At that time, I was asked to drive down to Aberdeen PG to pick up
some dust for a dust test we needed to conduct as weapons were jamming in the desert.
While at Aberdeen I met a fellow that had also been brought into the Ordnance Field by
L.F. Moore; he showed me around and got me loaded with bags of the test dust I was sent
to pick up. He then conducted me to the Branch’s Chief Officer and I had the shortest
job interview in history. I was offered a job as Small Arms and Ammunition Test
Director at Aberdeen PG. This was the icing on the cake; I had advanced from being a
avid shooter to the Product Engineering Section and then to the Design Section and now I
was going to be at the other end of the spectrum and conduct the testing.
At Aberdeen our unnoffical slogan was, “You make’em, we break’em.” And we did.
Depending on the test being conducted we fired one hundred rounds in a day to 10,000
rounds in a day. One day, I calculated we burned up $63,000.00 worth of ammunition
and were broken down four hours! We also did malfunction investigation of every
description and had to document everything. To a shooter a weapon will jam and that is
that; at Aberdeen, jammed weapons are broken down into sub-categories. For instance,
you can have failure to feed, bolt over base, failure to strip, failure to chamber, failure to
close, failure to lock, hangfire, failure to fire, failure to open, failure to extract, failure to
eject, etc. Testing stopped at each incident and a complete written report of exactly what
occurred was written up. We experienced very few misfires in testing. If memory
serves me correctly we had four misfires in 244,000 rounds on the M16A2 test and that
caused quite a stir. Hours and hours were spent on trying to determine the causes and
every lead was traced until confirmed or disproved. Here I learned that my friend L.F.
Moore had actually written much of the Test Operating Procedures that were still used at
Aberdeen long after he had moved on to RIA. But back to It Don’t Go Bang.
I have actually observed as many as 50+ misfires in about 1200 rounds of proof-firing
200 guns at a major firearms vendor plant. I got them let me take a sample of ammo and
sent it off for subsequent investigation by my primer engineer friends with measuring
microscopes and the other associated specialty tools for examining misfires and they
concluded there was nothing wrong with the primers. These guns went to a law
enforcement agency and the primer engineers sent a letter sent to that agency identifying
there was nothing wrong with the ammo and the person in charge of their ordnance area
accepted those guns for issue to the field! Why? Because that individual was a good
friend of the factory rep of the firearms company who arranged for nice donations of
guns as prizes for marksmanship competitions held yearly many of which were “won” by
this same individual.
As indicated, in the past at the Aberdeen Proving Ground I witnessed many very
interesting things; while I cannot speak for what is done now, when I was there misfires
were given special examination in an effort to determine the causes. I see no reason why
that would ever change.
Standards. Most everyone has experienced a misfire and a small percentage have
experienced a hang fire; that is when you hear the click, followed by the bang. Basically,
to give the reader some idea of exactly what is expected of US ammunition, the
government, Winchester, Remington and, I assume, Federal and CCI, have an allowable
misfire rate of one in a million assuming the primers were properly loaded and stored
(not exposed to heat, cold, moisture, oil etc). In reality the ignition rate is much better
than this, but I suppose one in a million was a good round number and they settled on
that. One manufacturer told me ten years ago, that in the previous year of in-house QA
testing they had experienced five misfires in 15,500,000 rounds that were not attributable
to the ignition mechanics; in other words, one misfire per three million plus rounds.
Primers need two things for reliable ignition: they need to be hit hard and and they need
to be hit at very high speed. Primers are tested in a drop fixture. They are placed in a
primer holding fixture and a steel ball is released to have an unretarded free fall before
striking the fixture. This testing is done with a 2 ounce steel ball dropped from a height
of 20 inches which will give 40 inch-ounces of energy when it arrives at the fixture.
A 20 ounce steel ball dropped from a height of 2 inches will give the same amount of
energy upon arriving at the fixture. So what is the difference? After all forty inch ounces
is forty inch ounces, well not exactly. Only problem is you will not obtain ignition on
the second scenario as the 20 ounce ball has not gained enough velocity prior to striking
the mechanism to initiate ignition. Thus the statement is they have to be hit fast and hard.
One without the other is useless.
In the industry, engineers endeavor to establish the All Fire Drop Height. That is the
lowest height the ball can be dropped and obtain 100% ignition reliability. In testing
primers they will then reduce the height the ball is released an inch at a time until they
achieve what is termed the All No-Fire Drop Height at which height no primers ignite.
Then the primer receptacle is replaced with a “copper” receptacle. Most shooters have
read a reference to “CUP” or Copper Units of Pressure. It is a copper cylinder made to
very precise standards.
In this instance they are also used in what is referred to as Copper Holders. You have the
one used in the fixture and then there are those that are made for each specific caliber. I
am blessed with owning a holder for 5.56, 308 and 30.06. Last one I had made cost over
$150.00. You may have seen one at a gun show and did not know what you were looking
at and the seller in all probability did not know what he had either. You are looking for a
item that looks exactly like a headspace gage but has a flat bottomed hole in the bottom
(where you would look for a primer in a loaded round) about 3/8” deep.
Generally there will be a smaller hole, say .075” drilled all the way through. This is to
push the copper back out (from the front) for bench inspection gage testing. There may
be writing on it saying what it is and there may not be. You kind of just have to know
from experience or in other words there is no writing on a hammer but you know it is by
the looks.
The copper is placed so as to receive the energy delivered by the striker nose and the ball
is dropped at the same height they experienced the all no fire condition. They may take 3
to ten samples. After removing the coppers they are placed on the anvil of a bench
inspection gage rigged with a sharp pointed contact (that will find the bottom of the
indent without touching the sides.) They record the indents in thousandths of a inch and
average the indents. My notes made during that time indicate the All No-Fire Indent (ON
COPPER) is 0.007”, while the All Fire Drop Height will exhibit 0.012” indent (ON
COPPER).
The government requirement for the l903, M1, M14 rifle is 0.020” (minimum) indent on
a copper. A quick comparison shows a substantial difference between the 0.012” All Fire
Indent and the 0.020” requirement on a weapon system. Or think of it this way. There is
nothing but air resistance to retard the 2 ounce steel ball falling however when you wrap
a striker with a spring or attempt to drive a striker down a tunnel (inside of a bolt) all
kinds of undesirable things can happen to retard the speed at which the striker impacts the
primer. So the weapon engineers in the government came up with the minimum
requirement of having our rifle small arms deliver 0.020” copper indent to overcome the
elements and conditions the weapon will see in the field. A safety margin to insure
reliability, in other words. This is basically true except the M16 family of weapons
wherein the requirement is 0.022” copper indent. There is only one small arms primer
harder to ignite than the 5.56MM round, that is the Cal. 50 BMG primer.
Striker Problems. It is fairly common knowledge that grit build-up in the striker
channel of a bolt rifle may retard striker velocity, and thus energy. Friction of the spring
rubbing along the striker can cause problems as well. A close examination of the inside
of a striker spring may reveal flat spots where the striker rubs against the spring as it is
seared up followed by sear disengagement. The travel distance is quite small but
nonetheless, the wear is apparent.
If you or a previous owner of your rifle have ever experienced a blanked primer (this is
where the primer appears natural except the area where you would expect an indent is
now gone leaving a clean cut hole there) and the blanked out material is nowhere to be
found, this is sign to check everything out. There is good liklihood it has traveled up
inside the striker opening and will in all probability wind up embedded on the rough
inner surface of the striker channel where it is pounded into the body of the bolt. The
inside of a bolt is rough (generally) as it is a drilled cavity. Once it is attached to the
striker channel it acts in the same manner as a disc brake and may instigate all kinds of
problems, i.e. hangfires, misfires, vertical dispersions etc It pays to keep the striker
channel clean and closely examined to eliminate build up of foreign materials/conditions
that will retard striker velocity.
Military weapon systems are subjected to conditions the average hunting rifle will never
see including complete submersion in mud or water and dust environments where the
dust is the same consistency as baking flower. However, hunting rifles are frequently
subjected to extreme cold and this may bring out lubrication problems relating to striker
energy. In a cold weather hunting situation springs tend to lose some energy. Couple
this with the wrong lubricant on the striker/spring assembly and the striker speed will be
severely retarded. Many a rifle has been sold because a guy took it hunting on a cold
morning, got a shot at a prize buck and CLICK, nothing happens. I remember a friend at
Picatinny Arsenal who worked in the machineshop area. He came to me one day and
said he had a Browning lever action .308 rifle he had purchased from his brother-in-law
for a hundred bucks because it would not fire when he was out hunting. I told him to
bring it in for a looksee and he did; it appeared to be a brand new rifle. In the warmth of
the building it sounded like there was sufficient striker action for reliable ignition.
We simply tore the rifle down, took it down to the plating shop and put the action
assembly down in the vapor degreaser to take the factory grease out of the striker and
action in general; from that day on it shot fine in cold weather. I don’t think the new
owner ever told his brother-in-law why it It Did Not Go Bang.
One last word on striker springs. I have seen bolts removed and torn down and found the
striker spring in pieces. I saw one broken in three pieces. Also before you get to misfires
and hang fires you may notice elevation problems. Remember All Fire was 0.012” and
All No-Fire was 0.007”? Well at 0.009” copper indent the primer engineers say you will
experience problems and I have seen new unfired commercial guns within the last 18
months delivered that exhibit 0.014” to 0.015” copper indent. Chances are if you have
printed this out, the paper it is printed on is 0.003” to 0.004” thick. Put two pieces
together in your fingers and you will have a feel for just how slim the margin is between
All Fire and All No-Fire.
Suppose you are going after Kodiak bear in cold weather with a .300 Win Mag. rifle you
just purchased. With the above in mind, wouldn’t this just give you lots of good warm
feelings of what may happen when you irritate one of these and he/she decides your time
has come? Talk about a good time to get a click instead of a boom, you are in prime
condition to wind up on the bear’s den wall. Considerng the guy that assembled your
rifle may have been a short order cook in Jersey last month just fills you with confidence,
doesn’t it?
Eccentric Firing Pin Impacts. If the above doesn’t give you a sick feeling in your
stomach then the following is really going to get your undivided attention. Yes folks the
above is the good news, stand by for the rest of the story.
We are supposed to be shooting center fire rifles correct? Well what exactly is the
definition of a center fire insofar as the firearms industry is concerned? We have all seen
and looked at the indents left in primers of center fire rifles. Most are off center just a
little right? In the government small arms field we called them Eccentric Firing Pin
Impacts. Frankford Arsenal (FA) did an exhaustive work on this many years ago and
published a magnificent document entitled Effects of Eccentric Firing Pin Impacts on
Primer Sensitivity. This study utilized several different calibers: .30 Carbine, Cal. 30, .45
ACP and .50 BMG.
Fixtures were fabricated to deliver striker impacts 0.020” and 0.040” off center of the
primer. Considering that most center fire rifles have striker nose diameters of
approximately 0.060” it basically offset the impact of the striker by one third the diameter
and two thirds. Remember earlier I stated the industry seems to prefer one half or 0.030”
offset based on a .060” diameter striker nose.
Drop testing was also conducted on 7.62MM cases at 0.004” 0.023”, 0.039” and 0.049”
off center hits. The results showed the primer sensitivity decreases as the striker blow
becomes more eccentric. Translated this means the furthur you hit off center the harder
the primer must be struck to insure reliable ignition! Now we know from the previous
discussion that there is a definite tendency for the striker spring to take a set and lose
energy over time, so if you are off center at the start, things can only go North from there.
The above testing was conducted with a four ounce ball delivering 64 inch ounces of
energy. Or in other words they really hit them hard! Now consider this scenario. This
testing was done with a free falling ball and was not hindered by any foreign material to
retard the striker velocity as described above. Couple this with decreased striker energy
and increased eccentric impacts the primer sensitivity will deteriorate and the misfire rate
will vastly accelerate.
Why are these offsets encountered? Several reasons for these offsets come to mind. For
instance the base dimension on a 308 Winchester case of commercial manufacturer is
.465-6” on new cases. Consider a factory chamber might be reamed at .470-471” in the
same area; there is offset potential right there as the extractor/ejector will force the base
of the case all the way to one side in the chamber. Next consider those cases you have
seen that really exhibit a swell at the base. I have seen them at .473” (on a fired case)
which is way over recommended max, but then again, who is watching the store? The
short order cook may have transferred to final inspection at the vendor’s plant.
On certain designs, the ability to drill the bolt way hole (in the receiver)and hold dead
center on that datum line is quite difficult. Not to mention the long hole drilled into the
bolt itself. Awful deep hole to drill without it wandering. Or say the bolt- way is off
.010” and he striker channel is off .010 andt the chamber on a 30 cal case is circa .473
diameter, that is about .025” off set right there! Attached there will be a picture of three
primers. The left primer example (which looks really good) was looked at with a 7X
glass and dial calipers measured the center of the actual indent to the outside of the
primer indicated this indent is off center .027”
Next the threads must be put in. I have seen much evidence that threads are not correctly
cut at right angles to the bore center line. A friend who actually was very knowledgable
about guns, worked for Remington. He told me to always look at a bunch of new rifles
where the barrel contacts the front of the receiver and if you can see where the barrel
appears to be jammed up tight on one side and not so tight on the other side leave it
laying. This is because the threads are not straight. Next you have the problem that the
bore may be off center in the barrel. This is quite common. If sufficent care is not taken
to insure the bore is centered and turned on centers and that the outside of the barrel is
cleaned up prior to threading there will be furthur offset to one side and a floating reamer
holder is going to follow the hole just as if it were a pilot hole which theoretically it is!
You have to keep in mind they are having to turn out hundreds of rifles per day and they
get paid piece rate. The politically correct term for this is “being on incentive”.
I was having trouble getting a barrel off a Remington 700 once. Called one of my friends
in Remington engineering and he suggested heating the receiver with a torch as the
receiver threads were probably so loose they coated the barrel threads with plumbers pipe
dope to keep it from coming loose. Sure enough after heating the receiver it screwed out
very easily and had gray pipe dope all over the threads. I have seen variations of thread
diameters in the range of 0.010” variation which is bound to affect several areas.
Pull up the Dave Manson Precision Reamers website Manson Precision Reamers | Gunsmithing Tools | Grand Blanc, MI
on your computer. Dave makes a kit that does a nice job of realigning the factory threads
and squaring everything up. Gunsmiths have coined a nice term for this: Blueprinting the
action. Translated, it means: make it like it should have been before leaving the factory.
I watched a friend use one of these on a 700 Magnum action. After the threads were
recut there was a marked difference in the primer indent on fired cases. The Manson
outfit brought the striker indent much closer to dead center.
Primer Storage. All the directions say to keep them in a “cool dry place”. One primer
engineer I know who is a shooter gets a bit more serious than that. I will pass on to you
his instructions/recommendations; I follow them. Buy primers by the case of 5000 and
try to get them right out of the factory. As soon as I get them they go into a 20MM
ammo can (which will hold four or five cases of primers). As I need primers I will go
and quickly open the 20MM can and remove 1000 and close the can as soon as possible.
These 1000 go into a 30 cal ammo can until used. I only open this can in the lowest
humidity conditions possible: winter or an air conditioned area in the summer. I remove
100 or 200 primers and place these in a plastic bag with a closure type arrangement. I
remove the primers, seat them, charge the cases, seat the bullets in as short a time span as
is practical. He even recommends if you are going to be hunting etc coat the ends with
clear nail polish wiping off the excess on a paper towel will leave the polish in place
around the circumference of the seated primer. He then places these in plastic boxes and
they go back into another GI ammo can for storage until he goes to the range.
Humidity is the worst enemy followed by lubricant contamination. I am aware of one lot
of government .308 Match ammo that malfunction investigation showed had oil
contamination from a over lubricated machine on the loading line. Another lot was
discarded when it was found to have oil in the primer mix that dropped in from a mixer
blending the ingredients.
In the government (military) when misfires occur with a ammunition lot or anything else
out of the ordinary a Quality Deficiency Report (QDR) is supposed to be filled out and
sent to Picatinny Arsenal for malfunction investigation. I was told by my Branch Chief
that the first thing done is to query the world-wide ammo control point as to how much of
that ammo lot remains in the system. When the report comes back that there is, say, three
hundred to four hundred thousand of that lot, they follow this with a World Wide
Destruct Advisory to destroy all ammunition of that lot number remaining in any depot.
Regardless of whether it is bad or not. It is cheaper to destroy that to investigate!
You may have noted that with the exception of match ammo, you have never seen
government ammo newer than three years old being used. This is because all the new
ammo goes into War Reserves in the ammo storage depots around the world and the
oldest ammo is then removed and sent to the troops which is generally three years for
some calibers and maybe forty years for others. Remember we went all through WW2,
Korea and Viet Nam with WW2 50 cal ammunition because so much had been
warehoused. Not to worry here folks, government ammo stored in its original unopened
cans has a MINIMUM expected life of 125 years. The trick is to never open the can until
time to use it. Once opened and exposed to the air, the shelf life drops remarkably
quickly.
Headspace. Another variable that needs to be considered is headspace. On most center
fire cartridges the headspace range on a new weapon is 0.006” from GO to NO-GO and
add another 0.004” for FIELD SERVICE (Total of .010” from GO to Field Service and
you may have a rifle on which the primer on a chambered round is sitting off the bolt face
.010” or just laying somewhere in between. Obviously when the striker comes along on
one of the loose as a goose jobs, some energy is going to be lost in driving he case
forward until it meets enough resistance to get ignition going. I chamber my rifles to
snug down on a GO gage or to where I have no freeplay in the bolt to reduce this
variable.
M16 Firing Mechanism. A little background on the M16 family of weapons. As
initially developed the M16 striker had a rather large head making the striker much
heavier than it is today. In those early days standard small rifle primers were being
loaded in the 5.56MM and when the troops dropped the carriers home the striker being
free in its run, was free to continue forward and strike the primer. With the cup being
normal dimensions and the striker heavy there were enough tic offs (as they were named)
to cause a Product Improvement Program (PIP) to be conducted to correct the problem.
At least two changes were made to eliminate this condition. First the head of the striker
was reduced to what it is today by removing much of the weight and secondly, the primer
cup for the 5.56MM was made heavier (thicker) to enable it to sustain the inertia hits.
The inertia phenomenon is not restricted to the M16. It is evident in the M1 Garand and
the M14 rifle which exhibit a small indent on the primer when the bolt is closed; however
they did not exhibit the tic off (actually fired) condition as the striker was much lighter.
I constantly read about accidental discharges from dropping the bolt carrier home on the
AR rifles. This condition can remedied by the use of Remington BR Primers or the CCI
Mil Spec Small Rifle Primer. Winchester makes a harder primer, the #41 Primer.
However, it is only available in the factory ammo and has not been made available to
handloaders. These are heavier (thicker) and thus designed for the AR series of rifles.
Perhaps other vendors’ primer cups are heavier to meet the mil spec for the 5.56MM
NATO, but I am not familiar with them.
I have read of some instances of supposed accidental firings where the M16 “fell over”
was “dropped” or some other story and someone was shot as a result. I do not accept
these explanations as I personally conducted the drop test on the M16A2 Rifle when I
was the Test Director on this weapon system for the Marine Corps in l982/3 time frame at
Aberdeen. Bullets were pulled and propellant dumped and the rifles were purposely
dropped on a steel test bed cast into cement at Aberdeen. I dropped and dropped and
dropped. Nothing. I held the rifle with the muzzle seven feet in the air and dropped it on
the muzzle. No fire. Finally I climbed up on a steel building and dropped it from 10 feet
in the air. No fire. Finally I got it to fire. I literally used it as if it were a speer and
threw it from the roof of the building to impact on the steel test bed directly on the
muzzle. It only ignited once in three tries if I remember correctly and the muzzle was
pointed at right angles to the planet. The flash suppressor on this rifle was severely
distorted to the point it need replacing. So the bottom line here is I don’t buy these I
dropped my M16 and it went off theory. It sounds feasible but is actually not likely
barring an Act of God. Now if it has ammunition with primers that do not meet the
milspec, the bolt is locked in the open position with a charged magazine inserted and then
it is knocked over causing the bolt to be released…. well maybe. I would like to see it
proved with repeatability. If the round is already placed in the chamber, no magazine in
place and the bolt dropped, now you have a different situation as the bolt encounters no
resistance as it travels into battery. With a charged magazine in place, bolt velocity is
retarded due to the energy required to strip the round from the magazine.
The author, Mark Humphreville is a Distinguished High Power shooter of many years who won the 1000yd. Wimbleton Match at Camp Perry a few years back shooting a pre-war M70 Winchester in 30-06 when most other competitors were using 300WM in actions of much more recent vintage. I had the pleasure of shooting with Mark on many occasions at Ft. Jackson and Ft. Gordon as well as Camp Perry. Mark lost the vision in his right eye in an accident many years ago and consequenty shoots the M70 left handed. To watch him shoot the rapid fire stages lefty with a right handed bolt gun is impressive. He is also a walking encyclopedia of small arms information as you shall see in the following text. The following article is a little lengthy, but worthy of your time for your small arms edification.
IT DON’T GO BANG-FIRES, HANGFIRES, MISFIRES AND SHORT ORDER
COOKS IN JERSEY
By Mark Humphreville
In looking over all the information I can find on the internet about “why it doesn’t go
bang” I notice that there is virtually no information for the average shooter to obtain the
knowledge needed to investigate these problems and possibly to correct the causes. I
hope to address that void with this article.
Background. While with the Army Small Caliber Lab and at Aberdeen Proving Ground
(APG) as Test Director Small Arms and Ammunition I was trained by some of the finest
minds in the business. They ranged from Primer Engineers that did nothing but play
with primers, mixes, etc their entire careers to Weapons and Ammunition Testing
Engineers at APG. What these folks taught me about small arms ignition reliability and
why they might or might not go bang was amazing to learn, and chances are I would have
never learned it anywhere else.
It must be understood, I grew up on the range so to speak. My father was a shooter, I
went to Camp Perry in l957 for first time and started loading ammo that same year. By
the time I finished high school, I had gone through over 25,000 primers. Like eveyone
else that shoots lots of ammo, has shot all his life and reads all that can be found, I felt I
had a pretty good basis of knowledge of what goes on in the gun business. I was
extremely lucky in having a great friend by the name of Larry Moore (Larry wrote many
articles for the shooter over his years) and he was chairman of the Configuration Control
Board at Rock Island Arsenal (RIA). He made the recommendation to the Army Small
Cal Weapons Lab that I be brought on board.
Upon arrival at the Army Small Cal. Lab, I learned in the first week that 20 years of
competitive experience was fun but did absolutely nothing to furthur my education in the
weapons field. When I went the the Small Cal Lab I was fortunate to make friends with
another bachelor who at that time had been in the ordnance field for 28 years; this guy
was an absolute walking computer filled with knowledge that he could bring up at the
mere mention of any ordnance subject. He talked incessantly and I listened intently. We
talked ordnance from the time we got in the car for the 37mile drive to work, all day at
work and on the way back to the big house we shared in Milford, Pa. At night we loaded
and on the weekends we went to the range. I worked side by side with him for over a
year and then got asked to come to the Special Projects Group working on the Dover
Devil Machinegun. At that time, I was asked to drive down to Aberdeen PG to pick up
some dust for a dust test we needed to conduct as weapons were jamming in the desert.
While at Aberdeen I met a fellow that had also been brought into the Ordnance Field by
L.F. Moore; he showed me around and got me loaded with bags of the test dust I was sent
to pick up. He then conducted me to the Branch’s Chief Officer and I had the shortest
job interview in history. I was offered a job as Small Arms and Ammunition Test
Director at Aberdeen PG. This was the icing on the cake; I had advanced from being a
avid shooter to the Product Engineering Section and then to the Design Section and now I
was going to be at the other end of the spectrum and conduct the testing.
At Aberdeen our unnoffical slogan was, “You make’em, we break’em.” And we did.
Depending on the test being conducted we fired one hundred rounds in a day to 10,000
rounds in a day. One day, I calculated we burned up $63,000.00 worth of ammunition
and were broken down four hours! We also did malfunction investigation of every
description and had to document everything. To a shooter a weapon will jam and that is
that; at Aberdeen, jammed weapons are broken down into sub-categories. For instance,
you can have failure to feed, bolt over base, failure to strip, failure to chamber, failure to
close, failure to lock, hangfire, failure to fire, failure to open, failure to extract, failure to
eject, etc. Testing stopped at each incident and a complete written report of exactly what
occurred was written up. We experienced very few misfires in testing. If memory
serves me correctly we had four misfires in 244,000 rounds on the M16A2 test and that
caused quite a stir. Hours and hours were spent on trying to determine the causes and
every lead was traced until confirmed or disproved. Here I learned that my friend L.F.
Moore had actually written much of the Test Operating Procedures that were still used at
Aberdeen long after he had moved on to RIA. But back to It Don’t Go Bang.
I have actually observed as many as 50+ misfires in about 1200 rounds of proof-firing
200 guns at a major firearms vendor plant. I got them let me take a sample of ammo and
sent it off for subsequent investigation by my primer engineer friends with measuring
microscopes and the other associated specialty tools for examining misfires and they
concluded there was nothing wrong with the primers. These guns went to a law
enforcement agency and the primer engineers sent a letter sent to that agency identifying
there was nothing wrong with the ammo and the person in charge of their ordnance area
accepted those guns for issue to the field! Why? Because that individual was a good
friend of the factory rep of the firearms company who arranged for nice donations of
guns as prizes for marksmanship competitions held yearly many of which were “won” by
this same individual.
As indicated, in the past at the Aberdeen Proving Ground I witnessed many very
interesting things; while I cannot speak for what is done now, when I was there misfires
were given special examination in an effort to determine the causes. I see no reason why
that would ever change.
Standards. Most everyone has experienced a misfire and a small percentage have
experienced a hang fire; that is when you hear the click, followed by the bang. Basically,
to give the reader some idea of exactly what is expected of US ammunition, the
government, Winchester, Remington and, I assume, Federal and CCI, have an allowable
misfire rate of one in a million assuming the primers were properly loaded and stored
(not exposed to heat, cold, moisture, oil etc). In reality the ignition rate is much better
than this, but I suppose one in a million was a good round number and they settled on
that. One manufacturer told me ten years ago, that in the previous year of in-house QA
testing they had experienced five misfires in 15,500,000 rounds that were not attributable
to the ignition mechanics; in other words, one misfire per three million plus rounds.
Primers need two things for reliable ignition: they need to be hit hard and and they need
to be hit at very high speed. Primers are tested in a drop fixture. They are placed in a
primer holding fixture and a steel ball is released to have an unretarded free fall before
striking the fixture. This testing is done with a 2 ounce steel ball dropped from a height
of 20 inches which will give 40 inch-ounces of energy when it arrives at the fixture.
A 20 ounce steel ball dropped from a height of 2 inches will give the same amount of
energy upon arriving at the fixture. So what is the difference? After all forty inch ounces
is forty inch ounces, well not exactly. Only problem is you will not obtain ignition on
the second scenario as the 20 ounce ball has not gained enough velocity prior to striking
the mechanism to initiate ignition. Thus the statement is they have to be hit fast and hard.
One without the other is useless.
In the industry, engineers endeavor to establish the All Fire Drop Height. That is the
lowest height the ball can be dropped and obtain 100% ignition reliability. In testing
primers they will then reduce the height the ball is released an inch at a time until they
achieve what is termed the All No-Fire Drop Height at which height no primers ignite.
Then the primer receptacle is replaced with a “copper” receptacle. Most shooters have
read a reference to “CUP” or Copper Units of Pressure. It is a copper cylinder made to
very precise standards.
In this instance they are also used in what is referred to as Copper Holders. You have the
one used in the fixture and then there are those that are made for each specific caliber. I
am blessed with owning a holder for 5.56, 308 and 30.06. Last one I had made cost over
$150.00. You may have seen one at a gun show and did not know what you were looking
at and the seller in all probability did not know what he had either. You are looking for a
item that looks exactly like a headspace gage but has a flat bottomed hole in the bottom
(where you would look for a primer in a loaded round) about 3/8” deep.
Generally there will be a smaller hole, say .075” drilled all the way through. This is to
push the copper back out (from the front) for bench inspection gage testing. There may
be writing on it saying what it is and there may not be. You kind of just have to know
from experience or in other words there is no writing on a hammer but you know it is by
the looks.
The copper is placed so as to receive the energy delivered by the striker nose and the ball
is dropped at the same height they experienced the all no fire condition. They may take 3
to ten samples. After removing the coppers they are placed on the anvil of a bench
inspection gage rigged with a sharp pointed contact (that will find the bottom of the
indent without touching the sides.) They record the indents in thousandths of a inch and
average the indents. My notes made during that time indicate the All No-Fire Indent (ON
COPPER) is 0.007”, while the All Fire Drop Height will exhibit 0.012” indent (ON
COPPER).
The government requirement for the l903, M1, M14 rifle is 0.020” (minimum) indent on
a copper. A quick comparison shows a substantial difference between the 0.012” All Fire
Indent and the 0.020” requirement on a weapon system. Or think of it this way. There is
nothing but air resistance to retard the 2 ounce steel ball falling however when you wrap
a striker with a spring or attempt to drive a striker down a tunnel (inside of a bolt) all
kinds of undesirable things can happen to retard the speed at which the striker impacts the
primer. So the weapon engineers in the government came up with the minimum
requirement of having our rifle small arms deliver 0.020” copper indent to overcome the
elements and conditions the weapon will see in the field. A safety margin to insure
reliability, in other words. This is basically true except the M16 family of weapons
wherein the requirement is 0.022” copper indent. There is only one small arms primer
harder to ignite than the 5.56MM round, that is the Cal. 50 BMG primer.
Striker Problems. It is fairly common knowledge that grit build-up in the striker
channel of a bolt rifle may retard striker velocity, and thus energy. Friction of the spring
rubbing along the striker can cause problems as well. A close examination of the inside
of a striker spring may reveal flat spots where the striker rubs against the spring as it is
seared up followed by sear disengagement. The travel distance is quite small but
nonetheless, the wear is apparent.
If you or a previous owner of your rifle have ever experienced a blanked primer (this is
where the primer appears natural except the area where you would expect an indent is
now gone leaving a clean cut hole there) and the blanked out material is nowhere to be
found, this is sign to check everything out. There is good liklihood it has traveled up
inside the striker opening and will in all probability wind up embedded on the rough
inner surface of the striker channel where it is pounded into the body of the bolt. The
inside of a bolt is rough (generally) as it is a drilled cavity. Once it is attached to the
striker channel it acts in the same manner as a disc brake and may instigate all kinds of
problems, i.e. hangfires, misfires, vertical dispersions etc It pays to keep the striker
channel clean and closely examined to eliminate build up of foreign materials/conditions
that will retard striker velocity.
Military weapon systems are subjected to conditions the average hunting rifle will never
see including complete submersion in mud or water and dust environments where the
dust is the same consistency as baking flower. However, hunting rifles are frequently
subjected to extreme cold and this may bring out lubrication problems relating to striker
energy. In a cold weather hunting situation springs tend to lose some energy. Couple
this with the wrong lubricant on the striker/spring assembly and the striker speed will be
severely retarded. Many a rifle has been sold because a guy took it hunting on a cold
morning, got a shot at a prize buck and CLICK, nothing happens. I remember a friend at
Picatinny Arsenal who worked in the machineshop area. He came to me one day and
said he had a Browning lever action .308 rifle he had purchased from his brother-in-law
for a hundred bucks because it would not fire when he was out hunting. I told him to
bring it in for a looksee and he did; it appeared to be a brand new rifle. In the warmth of
the building it sounded like there was sufficient striker action for reliable ignition.
We simply tore the rifle down, took it down to the plating shop and put the action
assembly down in the vapor degreaser to take the factory grease out of the striker and
action in general; from that day on it shot fine in cold weather. I don’t think the new
owner ever told his brother-in-law why it It Did Not Go Bang.
One last word on striker springs. I have seen bolts removed and torn down and found the
striker spring in pieces. I saw one broken in three pieces. Also before you get to misfires
and hang fires you may notice elevation problems. Remember All Fire was 0.012” and
All No-Fire was 0.007”? Well at 0.009” copper indent the primer engineers say you will
experience problems and I have seen new unfired commercial guns within the last 18
months delivered that exhibit 0.014” to 0.015” copper indent. Chances are if you have
printed this out, the paper it is printed on is 0.003” to 0.004” thick. Put two pieces
together in your fingers and you will have a feel for just how slim the margin is between
All Fire and All No-Fire.
Suppose you are going after Kodiak bear in cold weather with a .300 Win Mag. rifle you
just purchased. With the above in mind, wouldn’t this just give you lots of good warm
feelings of what may happen when you irritate one of these and he/she decides your time
has come? Talk about a good time to get a click instead of a boom, you are in prime
condition to wind up on the bear’s den wall. Considerng the guy that assembled your
rifle may have been a short order cook in Jersey last month just fills you with confidence,
doesn’t it?
Eccentric Firing Pin Impacts. If the above doesn’t give you a sick feeling in your
stomach then the following is really going to get your undivided attention. Yes folks the
above is the good news, stand by for the rest of the story.
We are supposed to be shooting center fire rifles correct? Well what exactly is the
definition of a center fire insofar as the firearms industry is concerned? We have all seen
and looked at the indents left in primers of center fire rifles. Most are off center just a
little right? In the government small arms field we called them Eccentric Firing Pin
Impacts. Frankford Arsenal (FA) did an exhaustive work on this many years ago and
published a magnificent document entitled Effects of Eccentric Firing Pin Impacts on
Primer Sensitivity. This study utilized several different calibers: .30 Carbine, Cal. 30, .45
ACP and .50 BMG.
Fixtures were fabricated to deliver striker impacts 0.020” and 0.040” off center of the
primer. Considering that most center fire rifles have striker nose diameters of
approximately 0.060” it basically offset the impact of the striker by one third the diameter
and two thirds. Remember earlier I stated the industry seems to prefer one half or 0.030”
offset based on a .060” diameter striker nose.
Drop testing was also conducted on 7.62MM cases at 0.004” 0.023”, 0.039” and 0.049”
off center hits. The results showed the primer sensitivity decreases as the striker blow
becomes more eccentric. Translated this means the furthur you hit off center the harder
the primer must be struck to insure reliable ignition! Now we know from the previous
discussion that there is a definite tendency for the striker spring to take a set and lose
energy over time, so if you are off center at the start, things can only go North from there.
The above testing was conducted with a four ounce ball delivering 64 inch ounces of
energy. Or in other words they really hit them hard! Now consider this scenario. This
testing was done with a free falling ball and was not hindered by any foreign material to
retard the striker velocity as described above. Couple this with decreased striker energy
and increased eccentric impacts the primer sensitivity will deteriorate and the misfire rate
will vastly accelerate.
Why are these offsets encountered? Several reasons for these offsets come to mind. For
instance the base dimension on a 308 Winchester case of commercial manufacturer is
.465-6” on new cases. Consider a factory chamber might be reamed at .470-471” in the
same area; there is offset potential right there as the extractor/ejector will force the base
of the case all the way to one side in the chamber. Next consider those cases you have
seen that really exhibit a swell at the base. I have seen them at .473” (on a fired case)
which is way over recommended max, but then again, who is watching the store? The
short order cook may have transferred to final inspection at the vendor’s plant.
On certain designs, the ability to drill the bolt way hole (in the receiver)and hold dead
center on that datum line is quite difficult. Not to mention the long hole drilled into the
bolt itself. Awful deep hole to drill without it wandering. Or say the bolt- way is off
.010” and he striker channel is off .010 andt the chamber on a 30 cal case is circa .473
diameter, that is about .025” off set right there! Attached there will be a picture of three
primers. The left primer example (which looks really good) was looked at with a 7X
glass and dial calipers measured the center of the actual indent to the outside of the
primer indicated this indent is off center .027”
Next the threads must be put in. I have seen much evidence that threads are not correctly
cut at right angles to the bore center line. A friend who actually was very knowledgable
about guns, worked for Remington. He told me to always look at a bunch of new rifles
where the barrel contacts the front of the receiver and if you can see where the barrel
appears to be jammed up tight on one side and not so tight on the other side leave it
laying. This is because the threads are not straight. Next you have the problem that the
bore may be off center in the barrel. This is quite common. If sufficent care is not taken
to insure the bore is centered and turned on centers and that the outside of the barrel is
cleaned up prior to threading there will be furthur offset to one side and a floating reamer
holder is going to follow the hole just as if it were a pilot hole which theoretically it is!
You have to keep in mind they are having to turn out hundreds of rifles per day and they
get paid piece rate. The politically correct term for this is “being on incentive”.
I was having trouble getting a barrel off a Remington 700 once. Called one of my friends
in Remington engineering and he suggested heating the receiver with a torch as the
receiver threads were probably so loose they coated the barrel threads with plumbers pipe
dope to keep it from coming loose. Sure enough after heating the receiver it screwed out
very easily and had gray pipe dope all over the threads. I have seen variations of thread
diameters in the range of 0.010” variation which is bound to affect several areas.
Pull up the Dave Manson Precision Reamers website Manson Precision Reamers | Gunsmithing Tools | Grand Blanc, MI
on your computer. Dave makes a kit that does a nice job of realigning the factory threads
and squaring everything up. Gunsmiths have coined a nice term for this: Blueprinting the
action. Translated, it means: make it like it should have been before leaving the factory.
I watched a friend use one of these on a 700 Magnum action. After the threads were
recut there was a marked difference in the primer indent on fired cases. The Manson
outfit brought the striker indent much closer to dead center.
Primer Storage. All the directions say to keep them in a “cool dry place”. One primer
engineer I know who is a shooter gets a bit more serious than that. I will pass on to you
his instructions/recommendations; I follow them. Buy primers by the case of 5000 and
try to get them right out of the factory. As soon as I get them they go into a 20MM
ammo can (which will hold four or five cases of primers). As I need primers I will go
and quickly open the 20MM can and remove 1000 and close the can as soon as possible.
These 1000 go into a 30 cal ammo can until used. I only open this can in the lowest
humidity conditions possible: winter or an air conditioned area in the summer. I remove
100 or 200 primers and place these in a plastic bag with a closure type arrangement. I
remove the primers, seat them, charge the cases, seat the bullets in as short a time span as
is practical. He even recommends if you are going to be hunting etc coat the ends with
clear nail polish wiping off the excess on a paper towel will leave the polish in place
around the circumference of the seated primer. He then places these in plastic boxes and
they go back into another GI ammo can for storage until he goes to the range.
Humidity is the worst enemy followed by lubricant contamination. I am aware of one lot
of government .308 Match ammo that malfunction investigation showed had oil
contamination from a over lubricated machine on the loading line. Another lot was
discarded when it was found to have oil in the primer mix that dropped in from a mixer
blending the ingredients.
In the government (military) when misfires occur with a ammunition lot or anything else
out of the ordinary a Quality Deficiency Report (QDR) is supposed to be filled out and
sent to Picatinny Arsenal for malfunction investigation. I was told by my Branch Chief
that the first thing done is to query the world-wide ammo control point as to how much of
that ammo lot remains in the system. When the report comes back that there is, say, three
hundred to four hundred thousand of that lot, they follow this with a World Wide
Destruct Advisory to destroy all ammunition of that lot number remaining in any depot.
Regardless of whether it is bad or not. It is cheaper to destroy that to investigate!
You may have noted that with the exception of match ammo, you have never seen
government ammo newer than three years old being used. This is because all the new
ammo goes into War Reserves in the ammo storage depots around the world and the
oldest ammo is then removed and sent to the troops which is generally three years for
some calibers and maybe forty years for others. Remember we went all through WW2,
Korea and Viet Nam with WW2 50 cal ammunition because so much had been
warehoused. Not to worry here folks, government ammo stored in its original unopened
cans has a MINIMUM expected life of 125 years. The trick is to never open the can until
time to use it. Once opened and exposed to the air, the shelf life drops remarkably
quickly.
Headspace. Another variable that needs to be considered is headspace. On most center
fire cartridges the headspace range on a new weapon is 0.006” from GO to NO-GO and
add another 0.004” for FIELD SERVICE (Total of .010” from GO to Field Service and
you may have a rifle on which the primer on a chambered round is sitting off the bolt face
.010” or just laying somewhere in between. Obviously when the striker comes along on
one of the loose as a goose jobs, some energy is going to be lost in driving he case
forward until it meets enough resistance to get ignition going. I chamber my rifles to
snug down on a GO gage or to where I have no freeplay in the bolt to reduce this
variable.
M16 Firing Mechanism. A little background on the M16 family of weapons. As
initially developed the M16 striker had a rather large head making the striker much
heavier than it is today. In those early days standard small rifle primers were being
loaded in the 5.56MM and when the troops dropped the carriers home the striker being
free in its run, was free to continue forward and strike the primer. With the cup being
normal dimensions and the striker heavy there were enough tic offs (as they were named)
to cause a Product Improvement Program (PIP) to be conducted to correct the problem.
At least two changes were made to eliminate this condition. First the head of the striker
was reduced to what it is today by removing much of the weight and secondly, the primer
cup for the 5.56MM was made heavier (thicker) to enable it to sustain the inertia hits.
The inertia phenomenon is not restricted to the M16. It is evident in the M1 Garand and
the M14 rifle which exhibit a small indent on the primer when the bolt is closed; however
they did not exhibit the tic off (actually fired) condition as the striker was much lighter.
I constantly read about accidental discharges from dropping the bolt carrier home on the
AR rifles. This condition can remedied by the use of Remington BR Primers or the CCI
Mil Spec Small Rifle Primer. Winchester makes a harder primer, the #41 Primer.
However, it is only available in the factory ammo and has not been made available to
handloaders. These are heavier (thicker) and thus designed for the AR series of rifles.
Perhaps other vendors’ primer cups are heavier to meet the mil spec for the 5.56MM
NATO, but I am not familiar with them.
I have read of some instances of supposed accidental firings where the M16 “fell over”
was “dropped” or some other story and someone was shot as a result. I do not accept
these explanations as I personally conducted the drop test on the M16A2 Rifle when I
was the Test Director on this weapon system for the Marine Corps in l982/3 time frame at
Aberdeen. Bullets were pulled and propellant dumped and the rifles were purposely
dropped on a steel test bed cast into cement at Aberdeen. I dropped and dropped and
dropped. Nothing. I held the rifle with the muzzle seven feet in the air and dropped it on
the muzzle. No fire. Finally I climbed up on a steel building and dropped it from 10 feet
in the air. No fire. Finally I got it to fire. I literally used it as if it were a speer and
threw it from the roof of the building to impact on the steel test bed directly on the
muzzle. It only ignited once in three tries if I remember correctly and the muzzle was
pointed at right angles to the planet. The flash suppressor on this rifle was severely
distorted to the point it need replacing. So the bottom line here is I don’t buy these I
dropped my M16 and it went off theory. It sounds feasible but is actually not likely
barring an Act of God. Now if it has ammunition with primers that do not meet the
milspec, the bolt is locked in the open position with a charged magazine inserted and then
it is knocked over causing the bolt to be released…. well maybe. I would like to see it
proved with repeatability. If the round is already placed in the chamber, no magazine in
place and the bolt dropped, now you have a different situation as the bolt encounters no
resistance as it travels into battery. With a charged magazine in place, bolt velocity is
retarded due to the energy required to strip the round from the magazine.