AR pistol build advice needed

[Coon]

I never had any thoughts of wanting an AR pistol, but with all of the attention the brace rule litigation has brought about, I decided to build one. I procured an SB3 brace and I’ve decided to just stick with .556 NATO caliber (or .223 Wylde). So my questions are mostly, what barrel length, twist rate and are there any tricks or things I should know, or avoid, what works best. All input is welcomed.
Thanks

 

[jetcycles]

Suppressed or nah? I like 10.5"ish 5.56 pistols.

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[Coon]

Not suppressed.

 

[toddnjoyce]

I don’t like 5.56 in pistols simply because ballistic performance drops off pretty sharply below 14”. They all tend to be loud AF, especially with a brake on them. Don’t ask me why people put brakes on AR pistols, but some do.

Having said all that, 10” is as short as I’d go.

ETA: twist rate is going to really be driven be projectile weight. 1:7 is an pretty versatile twist and performs well enough in a 10” barrel for 55/62/77gr projectiles.

 

[oldag]

Always tradeoffs to be made.

 

[smittyb]

Like @toddnjoyce said, anything under 12” unsuppressed with a 5.56 will be a very loud flamethrower.
I never understood why anyone would want a 10.5” 5.56 unless it was going to be shot suppressed 100% of the time.

ETA- This is coming from a guy who has several AR pistols.

 

[jetcycles]

I don’t like 5.56 in pistols simply because ballistic performance drops off pretty sharply below 14”. They all tend to be loud AF, especially with a brake on them. Don’t ask me why people put brakes on AR pistols, but some do.

Having said all that, 10” is as short as I’d go.

Definitely a niche weapon IMHO. I'm not sure you'd see any accuracy benefit with the Wylde chamber going pistol length, doubt you'd even need it given the limitations of a the platform in that configuration.

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[Lead Belly]

@Coon -

You better not be standing next to me at the range with that flamethrower!

Most guys use 300 blackout, 9mm or AK rounds for shorties. Build a 9mm AR if you want a challenging project.

 

[Coon]

I don’t like 5.56 in pistols simply because ballistic performance drops off pretty sharply below 14”. They all tend to be loud AF, especially with a brake on them. Don’t ask me why people put brakes on AR pistols, but some do.

Having said all that, 10” is as short as I’d go.

ETA: twist rate is going to really be driven be projectile weight. 1:7 is a pretty versatile twist and performs well enough in a 10” barrel for 55/62/77gr projectiles.

My only reason for not picking the .300BLK is that I don’t have anything else in that cal. and really don’t want to have to start buying another caliber ammo. As I typed that, I realized that I would probably have to buy or load specialized .556 loads for this pistol. So now I’m rethinking my caliber choice. The plan is for this to be a truck gun, but I really don’t want a pistol caliber. That ballistics table also has me rethinking my caliber choice.

 

[toddnjoyce]

…I realized that I would probably have to buy or load specialized .556 loads for this pistol.…

Not really, plain jane XM193 is decent enough out to 100yd for paper.

.…So now I’m rethinking my caliber choice. The plan is for this to be a truck gun, but I really don’t want a pistol caliber....

Used to be a truck gun was for varmints, critters, and ranch problems and folks had a venerable all purpose rifle for that. Today, most truck gun references I see are for self-defense type situations.

Ballistic performance against your target type and employment scenarios should be driving cartridge selection, not convenience.

As mentioned, some folks use x39 in AR pistols. I finally said f’ it and just sbr’d a .458S for what I wanted an AR pistol to do. Later, I dilly-dallied with making a 9mm AR and realized for me it was just toy with technical challenges and a purpose-designed SMG is now the way I would go if I wanted 9mm in a carbine/SBR application.

 

[10-96inTexas]

I have 2 pistols, a 5.56 and a 9mm. I much prefer shooting the 9mm. As said earlier, the 5.56 is loud. The 9mm is a lot of fun to shoot but to me, neither is very practical. I have a 11.5" pin and welded (to make 16") 5.56 that is a nice compromise.

No pics of the 5.56 but this is the 9mm. It uses regular 5.56 P-mags with Endomag 9mm inserts in P-mags and runs flawlessly.

 

[Coon]

No pics of the 5.56 but this is the 9mm. It uses regular 5.56 P-mags with Endomag 9mm inserts in P-mags and runs flawlessly.

View attachment 425194

Man, I'm so out of the loop. I didn't even know they made inserts like that.

 

[garabae]

I will second other posters in highly recommending 300 BLK for an AR pistol. Superior ballistics and unparalleled versatility.

 

[popper]

I have a 10" BO pistol, great truck/farm gun. RD sight works best. 110 vmax or 135FTX for bigger stuff, run from 1800 to 2k fps depends on weight.. Has a Kaw Valley linear comp that pushes sound away from me. Also plink with 145 PB cast or whatever else floats my boat. 20gr of powder is max so cheap to shoot.

 

[oldag]

I like the 7.2x39 AR pistols.

 

[popper]

Friend of GS has an AK pistol, lighter weight, clunky feeling and lots louder, factory ammo. More 'bulky' too. And that safety switch on the side, he accidently hits it often. I hit steel every time with 135gr FTX, he missed a few. Only AK I shot, had same problem, dang safety kept setting itself. And side mounted scope kept falling off.

 

[oldag]

Friend of GS has an AK pistol, lighter weight, clunky feeling and lots louder, factory ammo. More 'bulky' too. And that safety switch on the side, he accidently hits it often. I hit steel every time with 135gr FTX, he missed a few. Only AK I shot, had same problem, dang safety kept setting itself. And side mounted scope kept falling off.

I am not talking about AK pistols. AR format 7.62x30. PWS makes a great model, very reliable.

 

[CavCop]

For a 5.56, I recommend a barrel of 11.5” or longer for reliability, and a heavy buffer. A light buffer or shortest barrel and you will have reliability issues.

 

[sucker76]

If you're sticking with 556 then I'd suggest 10.5" 1:7 twist barrel. I think this gives the best compromise in performance and size. A linear comp/brake will be wanted to keep the blast at bay. A Noveske KX3 or Spikes Barking Spider or similar design are the ones I like. I have an older Barking Spider and like it. The Noveske is spendy. I think any liear comp with radial holes in it are defeating the purpose of it for the sake of looking cool.

 

[Coon]

For a 5.56, I recommend a barrel of 11.5” or longer for reliability, and a heavy buffer. A light buffer or shortest barrel and you will have reliability issues.

This seems to be the most advised setup for 5.56. I'll probably do just that. BTW, I liked your videos on the lower build. Thanks for the input.