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JohnC

Mega Arms AR15 Pistol Build

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This is just going to be a budget Mega Pistol build, so nothing too fancy.

So far it started life as:

749faa9920c497aff8ea56983f945ea6.jpg

Then I got the upper:

dbf8c4f81ec3176c6bb797553df7f024.jpg

Caught the Geissele SD3G on sale and figured it be perfect for a pistol build:

383bc371c2d29e73b3ea9fcc9891b5a5.jpg

0a85bb6c57e05c62753b4e6e93645db3.jpg

Then I picked up a ALG Defense LPK:

I screwed my bolt catch roll pin up and had to locate my other LPK kit to get that installed, so here is the next small bit of progress.

Mag release, safety, trigger guard, front take down pin and hogue grip installed.

fb2d9dffd65e5f1d85204f94f6f53d65.jpg

12bb4e1f7801182ab1a9cc85e2dd2025.jpg

Found my other LPK and installed bolt catch and Mega charging handle

667dd9470ec8ab2b8cdf1aa89ccc0c57.jpg

Now to order some more parts...


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I'm thinking about this really short buffer and bolt over the Sig Brace setup:

http://www.gunsmokeenterprises.net/product.sc?productId=5&categoryId=2

What do you guys think? Reliable? Goes bang and cycles properly? No FTF and FTE?

Also, looking for a 7 to 7.5 inch barrel with a free float keymod rail. What's out there? Links? Edited by JohnC

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I just built a pistol with an upper I bought from midstatefirearms.com. Inexpensive, great customer service and fast shipping!
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What caliber?

 

I will assume it is going to be a 7.5" 5.56. And while they are great range guns that are fun to shoot they are also very, very limited on their use as a defensive firearm. Energy levels are on par with most hot handgun

 

First, they are LOUD. And not just a little loud but painful and, for me anyways, it forces my eyes closed because of the muzzle blast. If you ever have to fire one inside a dwelling or, even worse, inside a vehicle it is probably the most miserable gun related thing you have ever done. I will not be around anyone shooting a 7.5" AR unless I have ear plug AND muffs on.

 

Second, the 5.56 needs barrel length to be effective in a traditional sense. Yes the bullet will damage someone but the damage will likely be very, very limited with a 7.5" barrel compared to even a 10.5" barrel. Ever inch extends the guns useable range.

 

If you MUST have a 7.5" gun for self defense at least get a twist, or ammunition, that is appropriate for the shorter barrel length if the gun may be used to save a life.

 

Velocity at the muzzle is already below the threshold for fragmentation so the bullet will NOT fragment no matter how close the "organic target" is. So the only wounding mechanism, other than a small hole, will be the bullet tumbling but only if the twist is slow enough. I would consider 9 twist to be the fastest twist for 7.5" guns. That way the bullets will at least tumble. If the barrel twist is too fast the bullets, because they will not tumble, will act just like a 22lr and will likely pass through.

 

Velocity with 55 grain bullets is ~2,350 fps which is well below the 2,650 fps most bullets need to fragment. So fragmentation being a mechanism for wounding is out of the picture. The next mechanism for wounding is the bullet tumbling but that will only happen when the barrel's twist rate is slow enough. With a 7 twist there is very little change of the bullet tumbling unless the target you are shooting at is feet deep.

 

With a 10.5" barrel the bullets will fragment but only out to about 25 yards. 11.5" is good to 25-50 yards. 12.5" is good to about 50-75 yards. 14.5" is good to about 75-100 yards. This is for FRAGMENTATION, not tumbling. So when the military decided to go to a 7 twist they took away the means of inflicting damage by tumbling. So the military is left with a rifle that has a twist too fast for the bullet to tumble and the velocity too low to fragment at anything but CQB distances. No wonder we are hearing reports of bad guys being shot several times and continuing the fight. I have personally seen the results of this when a bad guy was brought in after the had been shot in the hip and thigh area. He was walking on his own and actually had very, very little blood. It was an easily survivable injury despite being shot in an area that should have resulted in a femoral bleed.

 

But all this is academic at best if you are using quality varmint type rounds like the Hornady TAP rounds or even a quality hunting round would be better than FMJ in a gun with such a short barrel and a fast twist.

 

I have been considering doing a test but I need a couple of people to help. I can load up some M855 at velocities that simulate a distance of 100, 200 and 300 yards. Then shoot those bullets out of a 7 twist, 9 twist and 12 twist guns into water jugs to test and record the results. So if there is anyone in the Knoxville area who would like to get involved please let me know. To keep things as close to identical as possible I would like the guns to have 16" barrels and prefer ARs.

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I'd like to keep it as short, small and light weight as possible, but I am open to other calibers.

How would 300 blackout do?


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I'd like to keep it as short, small and light weight as possible, but I am open to other calibers.

How would 300 blackout do?


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It does excellent in 8-10" barrels. I have a mega pistol lower(my favorite forged lowers, best fit and finish around) and also a mega SBR. If you don't reload, 300blk is 30-50% more costly than 5.56. The plus side is you can run subsonic, if your gonna poke a hole at low velocity, 30 trumps 22 every time. Subsonic 300blk isn't anywhere near as obnoxious as .223 in a short barrel. I suggest a liner comp or blast shielded muzzle device to push noise and flash forward. I used Jim Timber's Simple Threaded Device prior to supressor ownership, and it works as described. I never used the sig brace either, the phase 5 tube is a tad shorter than a standard 6 position and works like it should.

http://www.amazon.com/gp/aw/d/B00I3SO76Y/ref=mp_s_a_1_1?qid=1440430157&sr=8-1&pi=AC_SY200_QL40&keywords=simple+threaded+devices&dpPl=1&dpID=41ADsb6BgvL&ref=plSrch
Phase 5 pistol buffer
http://phase5wsi.com/ar-15-complete-pistol-buffer-tube-assembly.html

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I just ordered a BCM forward assist assembly and ejection port cover assembly. More to come as parts are decided upon, ordered and come in. :up:

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I'm thinking about this really short buffer and bolt over the Sig Brace setup:

http://www.gunsmokeenterprises.net/product.sc?productId=5&categoryId=2

What do you guys think? Reliable? Goes bang and cycles properly? No FTF and FTE?

 

Quite bad experiences on that and some other short buffer systems on arfcom pistol forum over time, nobody really seems to consider them for a build anymore. Even if it works okay, now you got an oddball AR with no parts interchange within that subsystem. Can't tweak cycling with different weight buffers either, etc. And spent more money to boot.  I just wouldn't do it.

 

Plus, standard or longer buffer tube on a pistol is actually a good feature, just using it for 3rd point of contact against cheek improves stability and accuracy immensely.

 

- OS

 

edit: I see you've posted in arfcom pistol section. Everyone so far has overlooked your mention of the short tube setup since you only did link I guess. If you want specific input on that, mention it again with pic.

Edited by Oh Shoot

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Thanks for the info. Guess I'll do a Sig brace with mil-spec auto BCG.

What's a good reliable mil-spec auto BCG that doesn't break the bank?

I seen PSA had one for like $80 but at that price, I wondered what they cheaped out on.

What's your user name on AR15


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Thanks for the info. Guess I'll do a Sig brace with mil-spec auto BCG.

What's a good reliable mil-spec auto BCG that doesn't break the bank?

I seen PSA had one for like $80 but at that price, I wondered what they cheaped out on.

What's your user name on AR15

 

I'm Oh Shoot or OhShoot pretty much everywhere on gun related forums.

 

Any brand name M16 type carrier should be fine. PSA name brand one is fine usually call them "premium" I guess, though they sell some that aren't PSA branded. Bolt failure is fairly rare even with cheapos, but of course it does happen, but it also happens with expensive ones too.

 

Absolutely no reason to get a SIG or Shockwave brace unless you're gonna use it against the shoulder though (so make sure Mad Max Kingery ain't watching when you do ;))

 

- OS

Edited by Oh Shoot
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I have had the original Sug brace, the newest version and the Shockwave brace and out of all of the I like the Shockwave the best.

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Sig SB15 was supposed to come today, but for some reason it got delayed in Knoxville at UPS hub.

Will have more progress pics soon as that and other parts come in. :)


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I'm thinking about this really short buffer and bolt over the Sig Brace setup:

http://www.gunsmokeenterprises.net/product.sc?productId=5&categoryId=2

What do you guys think? Reliable? Goes bang and cycles properly? No FTF and FTHE?

Also, looking for a 7 to 7.5 inch barrel with a free float keymod rail. What's out there? Links?

Have you looked at this?

https://www.vltor.com/shop/a5-system/pistol-a5-the-vltor-a5-pistol-kit/

When I got my 16, I had nothing but troubles​ with sub 11.5" uppers with carbine, H, H1,H2, H3 buffers, I switched to the V5 set up and all the short stroking and bolt bounce issues disappeared and it doesn't matter what length of upper is used.

A 7.5" upper is uncomfortable up around your face... ​

 

 

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Parts came in.... Just need to slide brace on, but ran out of time.

903df7c83ced3b8b58224de1d59de6bb.jpg


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Edited by JohnC
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That Phase 5 buffer tube pushes the brace back way too far. I don't think I'm going to run it like this. I wanted this to be as short as possible for portability.

f125c1bd57d520a9ff459f065e77dbc5.jpg


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Edited by JohnC

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A standard pistol buffer tube is about as short as you will get with the Sig brace.

 

Yep, both the Phase 5 Hex tube and the KaK SB15 tubes add about 1.75" of length to the end of SB15 brace. Only diff is that the KaK tube extends inside to flush with the end of the brace while the shorter Phase 5 tube offsets it leaving a void inside.

 

Generally, this extra distance is a good thing for those who want to "redesign" their heater, though, which is 99.9% of the folks who buy a brace in the first place. :)

 

Btw, this whole thread is in wrong forum. ;)

 

- OS

Edited by Oh Shoot
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Well, guess if there is not a shorter tube for a brace out there I'll just stick with what I have.


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Well, guess if there is not a shorter tube for a brace out there I'll just stick with what I have.

 

Standard pistol buffer tube is shorter, essentially same length as carbine tube. SB15 (and SBX) brace is designed to fit any tube of 1.0-1.2" diameter. You don't need a special buffer tube for it.

 

The flange on the Hex and the KAK keeps the SB15 from moving forward, but the extra length is designed to make it more ergonomic to shoot from the shoulder for most folks by increasing LOP and moving yer schnoz back from the charging handle some, simple as that -- they just can't advertise it as such, especially after the most current "ruling".

 

- OS

Edited by Oh Shoot

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Well, got a Daniel Defense Lite II 7.0 Rail coming for the build from Rainier Arms. http://www.rainierarms.com/dd-lite-rail-ii-7-0

I also think I'm going to go with the Rainier Arms 7.5 inch pistol barrel, but still reading up on pistol barrels at this point. http://www.rainierarms.com/rainier-arms-selecttm-5-56mm-barrel-7-5-blk Edited by JohnC

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Have you looked at this?
https://www.vltor.com/shop/a5-system/pistol-a5-the-vltor-a5-pistol-kit/
When I got my 16, I had nothing but troubles​ with sub 11.5" uppers with carbine, H, H1,H2, H3 buffers, I switched to the V5 set up and all the short stroking and bolt bounce issues disappeared and it doesn't matter what length of upper is used.
A 7.5" upper is uncomfortable up around your face... ​
 
 


If this sig brace setup gives trouble, I'll definitely pick that up! :up:

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. Edited by bud

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JohnC I noticed your lower is marked "pistol". I want to build a pistol out of a stripped lower I have that is not marked pistol. Is that legal?

Yes. Stripped lowers are neither long gun or pistol. They are transferred as "receiver only" or "other".

If you have ever put a stock on that stripped lower however, the law states it cannot be a pistol after. Pistol marked lowers are a neat convenience, but not needed IMO


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....

If you have ever put a stock on that stripped lower however, the law states it cannot be a pistol after.

 

Bzzt. Stock has no significance. Even a completely finished virgin lower with stock attached is fine for a pistol build. And is transferred as "other firearm" via FFL.

 

No receiver (except NFA) can be anything other than a  GSA "firearm" until barrel or barrel and stock is attached.

 

In other words, this:

 

482769_1.jpg

 

is perfectly fine to make a pistol from, as long as it wasn't first built as a rifle. Remove stock, put upper on, you have a legal pistol. And yes, the carbine buffer tube left on it is also legit for a pistol.

 

 

- OS

Edited by Oh Shoot
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