RFI: AR Pistols

[HCM]

Thoughts:

10.5" barrel will provide all the longer-range performance you need and be more reliable without tuning. Go below that and you want to make sure the gas system is tuned to the shorter length. I believe that's just a matter of opening it up a little but don't quote me on that. You should get pretty much all the oomph out of a cartridge and can run at least up to 62gr with a 1:9 or 1:7 twist (memory may not be correct about 1:9 and that weight).

Shorter barrel is shorter length, of course, but you will lose some speed and even with 1:7 twist it's best to keep round weight below 60gr for best performance. I have a 7.5" barreled pistol that is my 'interstate bag gun' that I consider to be a 150-200 yard weapon max. It'll still leave a mark farther out I'm sure, but velocity suffers at the rate of approximately 100 fps per inch, IIRC, and running 52-55gr rounds I prefer to keep it close.

Arm braces be good. I have KAK shockwave but want to at least try the brand that I can't remember the name of right now--HATE it when that happens...

LAW folders good to reduce length for storage and carry. LAW folders not good because at best you get one shot before unfolding them, which might make it to slow to get into action in fullness. I have a covert bag that allows me to get away without one.

You might well find that the AR pistol doesn't gain you as much shortness as you thought. It's advantageous for other reasons, however. Here is a picture from the fourth book in my 'Gunfighting, and Other Thoughts about Doing Violence' series that has some comparisons. I have a big chapter on C-PDWs (Civilian-Personal Defense Weapons) in book, which category I put AR pistols into. (My AR pistol is 3rd one down in this photo.)
Attachment 24402

For 5.56, anything below 11.5” is going to have with reliability or durability. Yes, MK18’s can be made to run with 10.3” barrels but at the cost of durability and a greatly reduced service life compared to an 11.5” much less a 14.5”. There is a durability / service life cost when you “open up the gas port” to make things run. For 5.56 anything less than 10.3” is going to be a unreliable or beat itself to death in short order.


If you want an AR with a barrel below 10.3” do a 300 BO or a 9mm. 300 BO has a different pressure curve than 5.56 and shines in 8” and 9” barrel AR’s.

[Cool Breeze]

For 5.56, anything below 11.5” is going to have with reliability or durability. Yes, MK18’s can be made to run with 10.3” barrels but at the cost of durability and a greatly reduced service life compared to an 11.5” much less a 14.5”. There is a durability / service life cost when you “open up the gas port” to make things run. For 5.56 anything less than 10.3” is going to be a unreliable or beat itself to death in short order.


If you want an AR with a barrel below 10.3” do a 300 BO or a 9mm. 300 BO has a different pressure curve than 5.56 and shines in 8” and 9” barrel AR’s.

Any chance you know the length of an 11.5 inch AR pistol with LAW folder collapsed not including muzzle device (as that will vary from gun to gun)? I am trying to figure out OAL and if this is feasible for backpack carry like a vertx gamut.

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[HCM]

Any chance you know the length of an 11.5 inch AR pistol with LAW folder collapsed not including muzzle device (as that will vary from gun to gun)? I am trying to figure out OAL and if this is feasible for backpack carry like a vertx gamut.

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I have just such a beast - it may be a few days before I can drag it out of the safe though,

[Dave J]

Any chance you know the length of an 11.5 inch AR pistol with LAW folder collapsed not including muzzle device (as that will vary from gun to gun)? I am trying to figure out OAL and if this is feasible for backpack carry like a vertx gamut.

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Mine is just under 22" with a standard A2 flash suppressor, so call it 21" with no muzzle device.

[Crews]

As a reference, I have a 8.5” barrel on my SBR with LAW folder. With stock folded, without the muzzle device, it’s a hair under 17”. With muzzle device I ended up having to find a pack with a bare minimum of 19” inside space.

I ended up with a Mystery Ranch Urban Assault. It’s just about perfect. Just tall enough, wide enough to keep a mag inserted but still a pretty slim profile.







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[CR Williams]

For 5.56, anything below 11.5” is going to have with reliability or durability. Yes, MK18’s can be made to run with 10.3” barrels but at the cost of durability and a greatly reduced service life compared to an 11.5” much less a 14.5”. There is a durability / service life cost when you “open up the gas port” to make things run. For 5.56 anything less than 10.3” is going to be a unreliable or beat itself to death in short order.

If you want an AR with a barrel below 10.3” do a 300 BO or a 9mm. 300 BO has a different pressure curve than 5.56 and shines in 8” and 9” barrel AR’s.

I'm getting the 10.5" in barrel-length thought from people with a LOT more time behind an AR than I've even thought about having. They say it works just fine, runs just fine, shoots just fine. Haven't heard a word about greatly reduced service life. And to be honest, how many of us in the continental US are going to run an AR enough to make that a factor?

[johnnywitt]

They have a Mod 2 Tailhook with a quick adjust length of pull similar to an M4 stock but with a proprietary buffer tube.

Attachment 24410

So, the problem CURRENTLY with the GHW Mod 2 is that the charging handle will snag or hang up on the top of the stock & even if you file it down. Oh, and it's a pistol length buffer tube if you're running a DI Gun. Right now IMO the SBA3 with it's Carbine Length Buffer Tube might be the way to go with a DI Gun.
I'm going with Sig Vertis 11.5" 5.56 so that I can have a piston gun with a switch to adjust gas from suppressed to unsuppressed and a folder that will fire folded in an emergency.
Also, it will take any buffer tube so I can use the GHW MOD 2 if they resolve the issue with the stock or the SBA3, both, of course, minus the buffer springs & buffers. I plan to run the thing suppressed mostly so I like a piston gun with the adjustable gas & the ability to switch to 300blk later on maybe.

[johnnywitt]

For 5.56, anything below 11.5” is going to have with reliability or durability. Yes, MK18’s can be made to run with 10.3” barrels but at the cost of durability and a greatly reduced service life compared to an 11.5” much less a 14.5”. There is a durability / service life cost when you “open up the gas port” to make things run. For 5.56 anything less than 10.3” is going to be a unreliable or beat itself to death in short order.


If you want an AR with a barrel below 10.3” do a 300 BO or a 9mm. 300 BO has a different pressure curve than 5.56 and shines in 8” and 9” barrel AR’s.

I totally agree with you. A 300blk in a 9" barrel gun shooting supersonic ammo is pretty hard to beat. It's the ammo cost that gets me. 9mm is pretty much an outdated round in a LONG GUN for combat. I still like my suppressed UZI SMG & it is fun to shoot, but to defend your life, you 100% want a rifle round. An exponential increase in lethality.

[HCM]

I'm getting the 10.5" in barrel-length thought from people with a LOT more time behind an AR than I've even thought about having. They say it works just fine, runs just fine, shoots just fine. Haven't heard a word about greatly reduced service life. And to be honest, how many of us in the continental US are going to run an AR enough to make that a factor?

Just because you haven’t heard if it doesn’t mean it doesn’t happen. Particularly if you just open up the gas port till it runs as you suggested.

MK 18’s (10.3” barrel) require rebuilds at about 5k rounds. They will run a bit more but somewhere between 6k and 8k you will see issues like broken bolt lugs. Compare that with an average 15k service life fo pr 11.5”-14.5” guns and nearly 20k for 20” rifles.

It’s true there are plenty of gun fondlers out there, and most AR’s will see 100 rounds a year at best. However, PF is a shooters forum. If anyone will see high round counts it is PF members. 5k is not an insurmountable round count. A carbine classe or two and years worth of practice and local matches can add up to 5k pretty quick.

So I might be a firearms instructor and armorer who has a lot more rounds downrange with an AR over the past 30 years than you’ve thought of having or I might be a 14 year old girl posting from my moms basement. My advice costs exactly what you paid for it.

[HCM]

I totally agree with you. A 300blk in a 9" barrel gun shooting supersonic ammo is pretty hard to beat. It's the ammo cost that gets me. 9mm is pretty much an outdated round in a LONG GUN for combat. I still like my suppressed UZI SMG & it is fun to shoot, but to defend your life, you 100% want a rifle round. An exponential increase in lethality.

I would prefer a rifle round myself but the OP isn’t going into COMBAT. For home defense, a 9mm SIG brace pistol with a 30 or 33 round magazine isn’t going to be any worse than a conventional 9mm pistol. It is is cheaper shoot and can be safely shot on steel targets at much closer ranges than a true rifle round. If I had to choose one 8” or 9” Gunsite would be the 300 BO with supers.