AR15 and M16 pocket measurements??

[SugarBear1369]

AR lowers easy to do bud. I’ve done nearly a hundred. 19 of them are still in my possession as functioning weapons. Relax and just go to town.

Right on. I think I’m finally ready lol. Thanks a bunch for all the advice.

 

[SugarBear1369]

Only took him 81 to get it right!

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Nice cartoon lol!

 

[NavyVet83]

Only took him 81 to get it right!

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Nah. Ive been building AR’s a long time and over the years I’ve had to sell some off for money reasons, then I’ll hit a good spot and build more. lol

 

[SugarBear1369]

Hello again! Sorry for the disappearance lol. Some tools and stuff got caught up in the mail and work and the holidays all combined to put everything on hold for a few weeks. But I got everything together over the last few days and finally finished the first lower. I said I’d post some pics once done so here they are: let me know what you think.

 

[SugarBear1369]

Also, like I mentioned before, I want to do my lowers to m16 pocket specs and just not put the third hole for now, just in case I ever need to drill the third hole and put in select fire FCG parts the pocket will already be ready to go so I only need to drill the hole. I bought an adapter kit for the easy jig that does m16 spec pockets from finished AR15 pockets (no third hole though obviously) and I subsequently modified the finished lower to m16 specs. The pics of this are below: let me know what you think and how everything looks. I appreciate it. Thanks.

 

[SugarBear1369]

Two things I was wondered about the m16 pocket I did with the adapter jig. 1.) does the auto sear shelf look proper size/shape, etc.? And 2.) I don’t know how this happened since I was being quite careful but I somehow milled it down to between 0.47 and 0.48 inches (like 0.476 inches to be exact) instead of 0.450 inches, will this still be ok? Thanks.

P. S. I’ll post pics tomorrow of the m16 pocket adapter jig for anyone curious. Thanks again.

 

[Bobster]

These have been floating on my desktop waiting for your return. The pic rail is a bonus...

 

[SugarBear1369]

These have been floating on my desktop waiting for your return. The pic rail is a bonus...

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Awesome! Thank you. Yes I think I’m around those specs. My main pocket depth is a bit deeper, like 1.30” (or 1.29” something) and I think my other couple specs might be off a bit but I’m hoping they are all within the margin of error (which is apparently substantial according to what I read).

One thing I was wondering is with the m16 pocket I did does the auto sear shelf look like it’s the proper size and shape? and also it’s depth is 0.487” or something like that. I know it’s supposed to be 0.450” but somehow I over milled it a bit even with being careful. with the supposed large margin of error (plus I’ve seen different depths given from different sources varying from 0.450” all the way to 0.500”) do you think it’ll still be fine at the depth it’s at?

I’m gonna drill the hammer/trigger holes and safety selector hole soon as I finish fastening my drill press to my workbench.

Thanks again. It’s much appreciated and below are some pics of the m16 pocket jig adapter kit I used for anyone that might be interested. Thanks again.

Edit: thanks again for the pics and yes I know my return took forever lol. I can’t believe how much the holidays swamped me this year. At least it’s over, now I can get down to business. It’s nice to be back

 

[BillKilgore]

Congrats on milling first lower. It appears to be functional, but I have a few suggestions for your next lower.

1. Have a firm grip on the router when you start it up. They tend to wander until it is fully up to speed.
2. Always make sure the mill bit is not touching any surface when you start it. Touching any surface will cause the mill bit to jump around and nick the lower.
3. Extend the depth about 1/2 mm at a time. Cutting too much with each pass will create a rough surface in the FCG pocket. You will make more passes with this approach, but the router will be more controllable and the walls of the lower will be smoother.
4. When you finish milling a level, hold the router until the bit has stopped. This will also prevent nicks and scratches.

Let us know how she functions once you have it completed.

 

[SugarBear1369]

Congrats on milling first lower. It appears to be functional, but I have a few suggestions for your next lower.

1. Have a firm grip on the router when you start it up. They tend to wander until it is fully up to speed.
2. Always make sure the mill bit is not touching any surface when you start it. Touching any surface will cause the mill bit to jump around and nick the lower.
3. Extend the depth about 1/2 mm at a time. Cutting too much with each pass will create a rough surface in the FCG pocket. You will make more passes with this approach, but the router will be more controllable and the walls of the lower will be smoother.
4. When you finish milling a level, hold the router until the bit has stopped. This will also prevent nicks and scratches.

Let us know how she functions once you have it completed.

Awesome! Thank you very much for the congrats as well as the advice. Much appreciated. Everyone here has been invaluably helpful.

I will say also that you are absolutely correct (and the instructions that say to go low/slow as well are no exaggeration). I got a little greedy/impatient when it was going so smoothly and so easy and decided to try to start going deeper in every pass to save some time. Well, the flute tips of the end mill caught the edge of the pilot hole and shattered the end mill which then caught and chewed up everything. It chewed the side walls up pretty good and put a super deep gouge several layers deep in the floor of the main pocket. I was able to do a few passes around the side walls and clean those up as well as raise the height of the endmill and incrementally mill back down to depth which luckily milled the big gouge away (thank god). I’m ashamed to say I made this mistake not once but twice (yes I’m an idiot ).

I think what happened was I was allowing the edge of one of the flutes to touch the edge of the pilot hole and coupled with too much depth to begin with was causing the carbide endmill to just shatter outright upon firing up the router. And like you said, once that happened it made the router jump around like a ping pong ball, chewing and gouging everything in the process.

So I learned the hard way that it really is necessary to mill exceptionally low and slow with feed rate and depth of cut along with a zero point in feed and only contact the material at all once the router is on and the mill is up to speed. Thank god I bought several replacement speedmill/endmill combos before I started because I broke two of them, but at least I’ll never make those mistakes again (it was a costly but invaluable lesson).

Thanks again for all the help and assistance/info. Everybody. I certainly wouldn’t have been able to get this done without all of you.!

 

[SugarBear1369]

Congrats on milling first lower. It appears to be functional, but I have a few suggestions for your next lower.

1. Have a firm grip on the router when you start it up. They tend to wander until it is fully up to speed.
2. Always make sure the mill bit is not touching any surface when you start it. Touching any surface will cause the mill bit to jump around and nick the lower.
3. Extend the depth about 1/2 mm at a time. Cutting too much with each pass will create a rough surface in the FCG pocket. You will make more passes with this approach, but the router will be more controllable and the walls of the lower will be smoother.
4. When you finish milling a level, hold the router until the bit has stopped. This will also prevent nicks and scratches.

Let us know how she functions once you have it completed.

Also, yes of course, I certainly will keep you guys posted every step of the way how it turns out/functions in the end.

One question: if I wanted to clean up/smooth out the inside of the pocket how would I do that? Should I use some kind of attachment on my rotary tool like a burr or file or even a buffing or sanding wheel? (Or maybe even a small 1/8 or smaller endmill on the rotary)? Or maybe a fine grit hand file? Also, how much could I do before I need to worry about possibly taking too much material off and making the pocket too wide/walls too thin and messing up the dimensions/tolerances of the pocket itself? Again I know there’s a large margin of error on these things but even with that being so I’m sure it can eventually get screwed up if you get any part of it too severely out of whack. Thanks again for your time and all the help.

 

[BillKilgore]

I cleaned up a few rough spots on the side walls by manually sanding with the sandpaper wrapped around a paint stirring stick. This worked pretty well and allows you use progressively finer grits.

My 5D router jig will allow me to mill through the bottom of the pocket on the second depth setting if I am not careful. Which jig are you using?

Also, you mentioned drilling the selector and pin holes with a drill press. You should align the jig in your drill press without the lower in place. Make sure the top and bottom guide holes are in perfect alignment, then clamp the jig down. You do not want side holes out of alignment. With the jig in position, the drill bit should fall freely through both guide holes when you release it from the chuck.

Good luck.

 

[SugarBear1369]

I cleaned up a few rough spots on the side walls by manually sanding with the sandpaper wrapped around a paint stirring stick. This worked pretty well and allows you use progressively finer grits.

My 5D router jig will allow me to mill through the bottom of the pocket on the second depth setting if I am not careful. Which jig are you using?

Also, you mentioned drilling the selector and pin holes with a drill press. You should align the jig in your drill press without the lower in place. Make sure the top and bottom guide holes are in perfect alignment, then clamp the jig down. You do not want side holes out of alignment. With the jig in position, the drill bit should fall freely through both guide holes when you release it from the chuck.

Good luck.

Thanks! I’m gonna give the sandpaper a shot.

Also, I’m using the 80% arms easy jig gen 3 and the 80% arms freedom jig router that comes with it.

Will do as well with setting up the jig in the drill press. I’m thinking I’m gonna drill the holes out with one size smaller drill bits and then chucking ream them out to size (I’ll probably both drill and ream them with the jig on). I got pretty good at doing that (as well as just doing them to size with the correct size drill bits to begin with) on my practice block. It might seem like overkill lol but I bought a huge rectangle of 7075 aluminum raw material from McMaster-Carr and practiced drilling, reaming, milling and putting the rotary tools to it. It certainly helped me get a handle on everything though. Straight up drilling cones out pretty well but I’d have to say that drilling undersize and reaming out really does come out noticeably better and I feel like these holes need to be perfectly round and perfectly snug in shape and diameter (as well as being placed perfectly like you said).

Let me know what you think about the reaming and thanks again.

 

[BillKilgore]

The 5D and 80% Arms jigs are identical except for the color. I bought my jig, end mill bit and drill bits from Modulus Arms. The drill bits are exactly the right diameter. The trigger and hammer pins fit snugly and have not walked. If you feel more comfortable drilling and reaming to the appropriate size, go for it.

I have been milling AR lowers for only a year and I have a grand total of 2. There are many more experienced people on this forum, but I enjoy helping when I can.

 

[SugarBear1369]

The 5D and 80% Arms jigs are identical except for the color. I bought my jig, end mill bit and drill bits from Modulus Arms. The drill bits are exactly the right diameter. The trigger and hammer pins fit snugly and have not walked. If you feel more comfortable drilling and reaming to the appropriate size, go for it.

I have been milling AR lowers for only a year and I have a grand total of 2. There are many more experienced people on this forum, but I enjoy helping when I can.

Awesome, thanks! I tried it both ways and I did like how the reaming turned out but I did practice drilling the holes with just the drill bits as well and it did come out just fine that way too. I might just be overthinking it. I do like the reaming but at the same time I feel like the more steps I add the bigger chance of a screw up. I’m stuck between those two points.

I do have good drill bits and I also have the actual drill bits for the jig as well. I didn’t get them from modulus though, I got them from ghostgunjigs.com and I also have some aftermarket ones made for the jigs as well that I got from American gunsmith tooling. I got the speedmill/endmill combos from ghostgunjigs.com and I bought some zirconium nitride coated endmill replacements for them from AGT that I have not used yet.

Also, I appreciate all of the help. Thanks again.

Edit: I thought they looks similar too but I didn’t know they were Identical. Good to know. Thanks again.

 

[bkbrno]

Don't people know it's not a good idea to openly post some things?

Maybe it's the times we live in but all I see is an open invitation to draw people in to something that could go sideways real fast.

 

[SugarBear1369]

Don't people know it's not a good idea to openly post some things?

Maybe it's the times we live in but all I see is an open invitation to draw people in to something that could go sideways real fast.

What are you referring to?

 

[bkbrno]

What are you referring to?

First rule of Fight Club is never talk about Fight Club.