ar-15 pistol in 5.56

Dayman · Mar 19, 2014

With all the SBR and pistol threads on here I have finallly decided to get a lower I have sitting around together. Planning on a pistol build in 5.56. Can anyone give me recommendations on barrel length (10.5 or 7), gas tube length/setup (may affect hand guard choice). Seeing different length buffer tubes for pistol, will this effect cycling based on gas tube length? Is the buffer weight more of a factor.than the gas system? I know I cant have a vfg on a pistol but can I use an afg? Can you have a sling set up on a pistol? Sorry for all the questions, But this is the best site for what I would consider quality information. Thanks for all the help.

PapaBear · Mar 19, 2014

Dayman said:
With all the SBR and pistol threads on here I have finallly decided to get a lower I have sitting around together. Planning on a pistol build in 5.56. Can anyone give me recommendations on barrel length (10.5 or 7), gas tube length/setup (may affect hand guard choice). Seeing different length buffer tubes for pistol, will this effect cycling based on gas tube length? Is the buffer weight more of a factor.than the gas system? I know I cant have a vfg on a pistol but can I use an afg? Can you have a sling set up on a pistol? Sorry for all the questions, But this is the best site for what I would consider quality information. Thanks for all the help.

Seems the main reason to go 10.5 is for gas issues, but with the new pigtail gas tubes, and different buffer selections, a 7.5 can run just fine. I'm about to build mine, so I ordered a regular gas tube and a pigtail, and an H2 and H3 buffer. Figured at the range, with these parts, I can make one of them work and cycle correctly.

Still researching the afg issue, all the pictures I see have one, or a hand stop, installed.

Good luck!

By the way, if you need a barrel, there's a guy on armslist in Charleston with a lot of 10.5 barrels for sale....for a great price.

Tigerstripe · Mar 19, 2014

short bbl is a good time to try a piston upper. Andy just got a one piece bolt for his gas rod.

fordnut · Mar 19, 2014

I have had 5 AR pistols....and, I love them....but, they are a waste of ammo...I went to useing 20 round mags...You have a stupid grim on your face after you empty the mag...be it 20 rounds or 30 rounds the grin is the same....and you save 10 rounds of ammo.

I have had 10 1/2" and the 7 1/2" both. The 10 is far more accurate...but, if that is what you want...build a rifle.

The wide eyed look comes from the 3 foot flames of the 7 1/2" barrel...

The new Sig arm stock is the way to go if you want to hit anything. They come with an ATF letter of campliance...and you can control it...

If you go to AR-15.com, they have very good advice on the why and why nots of pistol bui;ding. I used them a lot on my first 2 pistols...

They are useless....but you will love one...

Steve

Gamecock24 · Mar 19, 2014

I went with a 7.5" bbl on my 7.62x39 pistol build. I haven't experienced any cycling issues with it using a regular pistol gas tube. If you feel like you need a pigtail gas tube search amazon they have some that are cheaper than the one from phase 5. I have also heard that a krinkov style muzzel device like the Noveske kx3 will help increase back pressure to improve cycling. There are also other cheaper ones of those too, but ones from ICE arms and MAS defense like the one I have will not increase the back pressure just direct the blast forward.

Oh and the Sig arm brace makes a pretty good shoulder brace too

bigfutz · Mar 20, 2014

Not to be a wet rag, but can you build a pistol AR on a lower that was not sold as a pistol lower? I mean I know you "can" but... TTYTT, how would you even distinguish a stripped lower for a rifle from a pistol?

On a positive note, Tiger McKee has been playing with pistol AR's lately. You might want to dig around on the 'net and see what you could learn from him.

PapaBear · Mar 20, 2014

If you buy a lower stripped, it is registered on the 4473 as "other." This means you can make it a pistol or a rifle.

Once it's a rifle, it's always a rifle. There doesn't need to be any markings saying it's a pistol.

So, if you have an AR and decide you want a pistol, you cannot convert a rifle lower into a pistol lower.....

Make sense?

bigfutz · Mar 21, 2014

PapaBear said:
If you buy a lower stripped, it is registered on the 4473 as "other." This means you can make it a pistol or a rifle.

Once it's a rifle, it's always a rifle. There doesn't need to be any markings saying it's a pistol.

So, if you have an AR and decide you want a pistol, you cannot convert a rifle lower into a pistol lower.....

Make sense?

I understand your English, but no - it doesn't make sense. I understood it as if you own a rifle, you can't own a short barrel upper unless you also own a pistol lower. IOW, get your pistol lower before (or at the same time) you get your upper.

bigfutz · Mar 21, 2014

Here's some reference info related to barrel length and gas system position:
http://ar15barrels.com/prod/gas-systems.shtml

armaborealis · Apr 4, 2014

The terminal ballistics on 7.5" bbls are awful in 5.56. If its a range toy, whatever. If it is not... then go longer.

2700 FPS is the velocity at which 5.56 (55/62 gr) reliably fragments. 10.5" bbls generate about 2700 FPS at the muzzle, so at room-length distances you might get frag. A 7.5" bbl will be well below fragmentation velocity at the muzzle. MK262 (77 gr) or TAP helps but you will still need at least 10.5" for reliable fragmentation to occur.

I opted for 12" which should give 2850 FPS at the muzzle. Much easier on the suppressor too, from what I've read.

If you go shorter than 10.5" I'd opt for 300 blackout, 7.62x39, or something else other than 5.56.