AR15 and M16 pocket measurements??

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SugarBear1369

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Hello. I know the jigs take care of this for you but I still like to know it just to be sure (and so I can measure it independently to make sure the jig did me right).

With that said:

Can anyone give me the depth measurements for the AR15 pocket (both front/main pocket and the rear shelf both high and low versions) and what the pocket width should be left to right both for the main pocket and the rear shelf (I think the rear is narrower than the front for the AR15, correct?)?

Also what are m16 pocket depths for both the pocket and the auto sear shelf? I’ve seen various depths from 0.9 inches to 1.25 inches. I believe m16 pockets are uniformly the same depth all around the whole pocket except for the auto sear shelf nub, is this correct? And I’ve seen various auto sear shelf/nub depths from 0.40 to 0.46 inches. And what is the width on an m16 pocket. I’m pretty sure that’s uniform for the whole pocket too, right?

Lastly what length front to back are fire control pockets? ( I would think both AR15 and M16 pockets would be the same front to back lengths, correct?)?

I appreciate any help, as always.
Thank you

- Kris
 
This is probably not what you were looking for but I had it handy. :D

I think most everyone mills the pocket for M-16s. The only issue with ATF would be the "third pin hole" the burst mech rotates on.

PS: dimensions are in God's measuring system... ;)
 

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  • ar15_receiver.pdf
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Bobster said:
This is probably not what you were looking for but I had it handy. :D

I think most everyone mills the pocket for M-16s. The only issue with ATF would be the "third pin hole" the burst mech rotates on.

PS: dimensions are in God's measuring system... ;)
Click to expand...
Cool! Thanks for that. I can’t get it to download though. I’m trying with an iPhone so I’ll try with my desktop when I get home.

Also, yeah my thoughts exactly. I want to do full auto bolt carriers and m16 pockets on all my guns just no third holes or m16 fcg parts (until SHTF). This way when the time comes I just need to swap out fcg parts and drill the third hole. I don’t need to worry about the pocket and milling and all that stuff. That’ll already be taken care of.

I picked up the easy jig gen 3 and the freedom jig router so I can use a router for pockets but as you probably know that jig doesn’t do m16 pockets, so I bought this 3D printed m16 pocket adapter kit that’s supposed to fit the easy jig gen 3, 5D tactical pro, etc. but it’s instructions seem a bit off to me. They seem like they are calling for a stepped pocket where the whole left hand side of the pocket from front to back is milled down to 0.9 inches or so and the whole right hand side of the pocket is milled down to 0.46 inches. This sounds totally absurd to me. Both the pocket shape that would make as well as the 0.9 inch depth. I thought an m16 pocket was basically a uniform rectangle except for that small indent/nub style auto sear shelf on the rear right hand side and I thought only that little nub itself went to 0.46 inches and the whole rest of the pocket (not just the left hand side) uniformly went to 1.25 inches all around (not 0.9 inches).

The other jig I have is the machinegunguy AR15 jig and it calls for those dimensions (1.25 inches uniformly around a rectangle except for 0.46 inches on that small nub of an auto sear shelf) but that jig calls for me using the milling top to outline the pocket then taking the jig off, putting it in the milling machine vise, and free hand milling out the outline to the prescribed depths. Or to use a drilling top to drill it all out with a drill press (which would probably take forever).

I was thinking of using a hybrid of both worlds if you will. Using the easy jig first to make an AR15 pocket with the router and then using the machinegunguy jig to trace the m16 pocket over that and then use the drill press with the end mill in it to widen the rear of the pocket (around the auto sear nub/shelf) and then take the depths down where they need to be all around (1.25 inches for the whole pocket and 0.46 inches for the nub/shelf), then putting either of the jigs back on to drill all the holes except the third hole.

What do you think? Thanks
 
Also, am I correct in my understanding that the m16 pocket is supposed to be an even rectangle all around except for the little auto sear nub and that the whole rectangular pocket is supposed to be 1.25 inches in depth uniformly and that the auto sear shelf/nub is supposed be 0.46 inches in depth? Or am I incorrect on this?

Also, what do you guys use to measure depth of pockets and shelf’s independently of the depth stops on the tools themselves? Do you use digital calipers? Something else? Thanks again.
 
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SugarBear1369 said:
I can’t get it to download though. I’m trying with an iPhone so I’ll try with my desktop when I get home.
Click to expand...

You don't have a free pdf viewer on your phone? :eek: ;) LINK I have maybe 25? apps TOTAL and that is one of them... :)


acrobatapp.JPG
 
Bobster said:
You don't have a free pdf viewer on your phone? :eek: ;) LINK I have maybe 25? apps TOTAL and that is one of them... :)


View attachment 26008
Click to expand...
Thanks for that. I’m gonna get it downloaded now cuz I never got around to getting on at the house. My brothers kids are over for the weekend so it’s insanity right now.
 
Ok. So, I've looked at it now plus I've studied the easy jig more so now I understand how that works as well and I think I've got it. Someone please correct me if I'm wrong.

It looks like on both the AR15 and the M16 the actual pocket is placed in the same area on top of the receiver and is the same length and width. Also, it seems that the main pocket (like the front 2/3 or so roughly) is the same depth in both versions (1.25 inches more or less) and the same shape. it seems to me that the only difference between the two versions is the tapered/narrowed rear portion, or tail, of the AR15 receiver (like the back 1/3 or so). Is this correct?

Also, it seems to me that once you have a completed AR15 pocket, since everything else is the same, you could just do the pocket to AR15 specs first with the easy jig and then just modify that back tail portion of the AR15 receiver to M16 specs, yes? And it looks to me that the only two modifications required would be taking the wall of the left side of the rear pocket of the AR15 pocket off (where it tapers in to create the narrowing) so that is is flush/even with the wall of the front of the pocket (basically getting rid of the tapering completely so that the entire pocket's dimension is even like a rectangle) and bringing that down to a depth of at least 0.950 inches, and then bringing the right hand side down to a depth of 0.450 inches, and I think that's it. Am I correct on that? If so, I could probably free hand that with the drill press or my rotary tool with rotary file (and just check depths with a depth gauge micrometer) after I complete the pocket to AR15 specs with the easy jig. Please let me know.

P. S. on the rear right hand side, for the auto sear shelf of the M16 pocket, I take that side down to 0.450 inches in depth but do I evenly take that whole right hand side shelf down to that depth? like is it already the proper size and shape for the auto sear shelf and just needs to be lowered or do I need to alter it's size and/or shape as well as take it down to 0.450 inches depth?

I appreciate any and all help and I appreciate everyone's continued assistance and patience so far. I know I'm slower than molasses lol but I think I've finally almost got it.

-Kris
 
If you just need the thing to work get the trigger holes spot on and the pocket walls. I hesitate to say but don't over think it most of the dimensions are not critical. Junking your first one won't be the end and you probably can fix it with JB weld most likely. Go for AR15 spec there are like 10 different pocket configurations to visit another day.

For tools:

Use the jig in its OEM config for measuring tools look into these for depth use.
www.shars.com

0-6" Depth Micrometer

www.shars.com www.shars.com
or better in this case for everything.
www.shars.com

Aventor 6" Large Screen IP54 Electronic Caliper

www.shars.com www.shars.com
 
Last edited:
rodm1 said:
If you just need the thing to work get the trigger holes spot on and the pocket walls. I hesitate to say but don't over think it most of the dimensions are not critical. Junking your first one won't be the end and you probably can fix it with JB weld most likely. Go for AR15 spec there are like 10 different pocket configurations to visit another day.

For tools:

Use the jig in its OEM config for measuring tools look into these for depth use.
www.shars.com

0-6" Depth Micrometer

www.shars.com www.shars.com
or better in this case for everything.
www.shars.com

Aventor 6" Large Screen IP54 Electronic Caliper

www.shars.com www.shars.com
Click to expand...
Awesome! Thank you.

Sorry about my late responses been crazy with the kids and now the holiday coming up I’ll have like 10 kids in my house for the next week between my brothers and my sisters family coming over so it’s about to get hectic lol.

Yeah that was one of my biggest problems. I wasn’t sure if the measurements/dimensions had to be like spot on exact or if they had wiggle room for error and didn’t need to be exact especially if I didn’t care if it looked rough. Like you said I figured the only thing needing to be exact was hole placements (for obvious reasons) but I have the jig for that. I just wasn’t sure about the auto sear shelf, I have depth (.450) but shape and size not so much. Oddly enough, I thought the same thing you said about JB Weld lol, using it to fix the auto sear shelf if I screwed it up lol.
 
While I’m ordering the calipers, depth gauge etc this week I want to order a set of drill bits. Some end mills and chucking reamers too but I haven’t found ones I’m gonna get yet for those.. I have found drill bits though. These ones kept popping up in my research for being good for drilling aluminum (especially for precise holes in aluminum).

www.menards.com

Masterforce® Axis Point™ Cobalt Twist Drill Bit Set - 29 Piece

Masterforce® 29 piece set of cobalt M35 industrial grade high-speed drill bits include multiple sizes and round or tri-flat shanks that last ten times longer and provide superior, specialized performance. AXIS specialty point starts ten times faster. 135-degree split point provides faster...
www.menards.com www.menards.com

They make a titanium set too (this one’s cobalt) that’s pretty much identical other than being titanium.

Anyone use these? Do they look good? I appreciate any help as always. Thanks again.

- Kris
 
SugarBear1369 said:
While I’m ordering the calipers, depth gauge etc this week I want to order a set of drill bits.
Click to expand...

A caliper is also a depth gauge... :)

Cobalt are if you plan on drilling hard steels. You are better off saving your money and getting dedicated bits for alum. Al is "sticky" so you want a "smooth" bit less likely to gall. 135° is sort of shallow, 118° is better, more aggressive.
 
The minimum would be the calipers the other is just extra stuff. A handy attachment for the calipers would be a base attachment but its extra to. For drills I would splurge on these and buy name brand ones they will be sharp and drill to size. You don't need chucking reamers if you keep the drill RPM very slow and let the drill find its way use Kerosene if you need lube. What are you going to use to drill the holes?

www.shars.com

Depth Base Attachment for 6" 8" 12" Aventor Digital Caliper

www.shars.com www.shars.com

Good drills
www.ebay.com

Chicago-Latrobe 5/32 150ASP 45610 JOBBER HSS Drill 12pcs NEW | eBay

Condition: NEW.
www.ebay.com
 
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Shug.... I admire a man who is thorough but since we are all friends here ... you might be overthinking this project from a tooling perspective. It's a lower. A one eyed triple amputee could do it with his left foot and a cheap drill press or router. The tolerances are not that tight. Jump in the pool and enjoy the water! You'll have a better perspective on what tooling you need after making the first and second one.

When I did the first one without the benefit of a mill and zero experience, I put masking tape on the end mill at the appropriate length so I wouldn't cut too deep. Worked fine. If you are off by a millimeter or two on the pocket it wont matter. Just get the trigger holes right and use a new bit. Trust the jig - it makes this easy.

When I was doing my first one, I also had some anxiety about having all the right tooling and having all the right parts together in advance. It was harder back then. Fewer vendors, sparse online help. Somebody advised me to get a plastic lower to use as a practice run. If you mess it up, throw it away. I didn't go that route but it's not a terrible suggestion.

Happy Thanksgiving!
 
Last edited:
Bobster said:
A caliper is also a depth gauge... :)

Cobalt are if you plan on drilling hard steels. You are better off saving your money and getting dedicated bits for alum. Al is "sticky" so you want a "smooth" bit less likely to gall. 135° is sort of shallow, 118° is better, more aggressive.
Click to expand...
Thanks for this! I went to McMaster carr and just picked out some HSS that were 118 and for aluminum. Thanks again. Much appreciated.

P. S. Also, good to hear about the depth gauge/caliper lol. That saves me some cash.
 
rodm1 said:
The minimum would be the calipers the other is just extra stuff. A handy attachment for the calipers would be a base attachment but its extra to. For drills I would splurge on these and buy name brand ones they will be sharp and drill to size. You don't need chucking reamers if you keep the drill RPM very slow and let the drill find its way use Kerosene if you need lube. What are you going to use to drill the holes?

www.shars.com

Depth Base Attachment for 6" 8" 12" Aventor Digital Caliper

www.shars.com www.shars.com

Good drills
www.ebay.com

Chicago-Latrobe 5/32 150ASP 45610 JOBBER HSS Drill 12pcs NEW | eBay

Condition: NEW.
www.ebay.com
Click to expand...
I appreciate the info. Thank you. I wind up going to McMaster Carr and used the filters to find HSS bits for aluminum that were from USA or other quality places (Germany etc). No Chinese bits. I think Chicago Latrobe was one of the brands McMaster had. Thanks for that info as well.

Btw, I will be using the easy jig and a drill press to do the drilling. Thanks again.

- Kris
 
Bongo Lewi said:
Shug.... I admire a man who is thorough but since we are all friends here ... you might be overthinking this project from a tooling perspective. It's a lower. A one eyed triple amputee could do it with his left foot and a cheap drill press or router. The tolerances are not that tight. Jump in the pool and enjoy the water! You'll have a better perspective on what tooling you need after making the first and second one.

When I did the first one without the benefit of a mill and zero experience, I put masking tape on the end mill at the appropriate length so I wouldn't cut too deep. Worked fine. If you are off by a millimeter or two on the pocket it wont matter. Just get the trigger holes right and use a new bit. Trust the jig - it makes this easy.

When I was doing my first one, I also had some anxiety about having all the right tooling and having all the right parts together in advance. It was harder back then. Fewer vendors, sparse online help. Somebody advised me to get a plastic lower to use as a practice run. If you mess it up, throw it away. I didn't go that route but it's not a terrible suggestion.

Happy Thanksgiving!
Click to expand...
lol I hear you man. I know I get obsessively thorough about every new undertaking I pursue. My wife kids me and says I’m like a troll whenever I have a new project; I never leave the basement or my home office/workshop like a troll under his bridge lol.

But yeah I agree, it’s time to just get the rest of the stuff and get to it. Thanks for the advice too, it’s greatly appreciated.

- Kris
 

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