Barrel lengths for AR pistols

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American_Fusilier

American_Fusilier

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I'm building an 5.56 AR pistol, and I'm planning on putting a 10" barrel on it, mostly because I can use a carbine length gas system, and a regular buffer, etc.

Are there any reasons why I should go with a shorter or longer barrel?

What are your guys experiences?
 
I was asking myself the same question not too long ago. I wanted to go shorter than 14.5 but wanted to stay with 5.56 and didn’t want to cripple it.

I was actually kind of teetering between 10.5 and 11.5 on the lengths when a friend of mine told me that all he ran in the military and with swat was the 10.5 and they ran fine, I went with it.

I did get to run an 8” yesterday. The guy running it put a few hundred rounds through it and didn’t have any problems. I just wish I had my chrony set up. It was a sexy little setup.
 
I have a 7" and a 10.5". the forend on the 7" is quadrail, so it is bulky. Eventually I will replace it with an M-Lok forend like my 10.5" has. I like the 10.5" better overall.
 
For not crippling performance, barrel length depends on ammo weight and specific bullet brand, as some bullets that weigh the same are hotter than others. For 55 Gr FMJ (XM193 specifically), 10.5" barrel minimum. 62 Gr Bullets, 13" Barrel minimum. For 75 Gr Bullets, has to be 16". My reasoning is 2700 FPS is 100% consistent hydrostatic shock, and those are the barrel lengths that generally require bullets at different weights to hit that velocity.
 
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For me when you get less than 10 or so inches on a 223/5.56 it turns into a novelty, for example 7-7.5" barrels. Blasty, poor performance etc. But, I see them everywhere so someone has to be buying them...

BCM MKII 12.5" feels right to me. And when you screw a can onto it it's still about the same length as an 18" barreled upper. I have a 10.5" as well, its not bad at all. The 2 inches seems negligible but the other longer one just seems to run smoother/better. In my experience the longer barreled "pistols" (10-12.5") can be much more accurate than you would think.
 
I've put more than a few rounds through a 10.5 and 11.5 inch 5.56 upper. Using the same ammo, the 11.5 shoots a little flatter and hits a little harder out to 300 yards.

If going shorter than that, a 300 BLK is a more practical choice.

I say, get the length you want and shoot it a lot. If you don't like it, pull the barrel, sell it and try another.

What barrel length are you most interested in?
 
My local gun shop sells AR pistols in 7.5, 8.5, and 10.5 barrel lengths. Give or take a little measurement based on maker. The 10.5 felt most balanced in my hand. As I understand it they usually have the least blast/flash of the typical AR pistol lengths. It is the length I am leaning toward the most when/if I put mine together.
 
10.3-11.5" if you want short,but not too short, I personally would not go below 10.3". Makes a difference what barrel you use ,if the mfg set it up correctly for the short barrel, correct gas port. I shot a friends PSA 10.5" that shot harsh, more recoil, didn't seem as smooth as my Colt 10.3" or BCM 11.5", it has been reliable so far. My buddy's gun used a CAR buffer and showed him that by popping in a H2 buffer it helped slow things down and smooth it out, but I still feel the PSA was over gassed.
I use better recoil springs like the Brownells Chrome silicon springs, they seem to be better than regular old USGI type music wire springs. When I run out of these I will be switching to a Tubb spring.
 
I have 3 shorties. two in 5.56, one 10.3", and one 10.5", and an 11.3" .300 Blackout. I got the .300 BO for a single job, Home defense. The .300 with the 110gr Barns VorTX is a great defensive weapon in a small package for a short range gun, but it's a SBR. The other two are pistols, and travel around more freely, and shoot less expensive ammo. The 5.56 gives up a bit in the short barrels though. I wanted the hardest hitting round for my home defense, but ammo for the .300 is WAY more expensive. The 5.56 is still pretty good for short range use out of a 10.3 so for general use, I'm very happy with the 2 pistols for everything else. One of them would be my normal go-to guns, as the ammo to feed them is much less expensive, and almost as good.

10.3" DD.
pcJaQXd.jpg

10.5" PSA based Frankengun
VTdJYtt.jpg
 
Browning said:
Longer barrels help the bullet to fragment or with soft point or hollow point ammo to at least open up and mushroom. This increases the wound size.

View attachment 898424
Click to expand...

Cool, according to that graph, 10.5 is a sweet spot in terms of velocity and compactness.

Man, those are some sexy looking toys. I was online on PSA's website last night about to pull the trigger on a 10.5 upper that they have on sale for $150. Gunshow this weekend and was gonna grab a pistol lower. Checked my play account to see if I needed to move some money around and discovered a bunch of unauthorized charges on my card. Pfft, had to get on the phone with the bank and cancel the card. Should I take this as the universe trying to tell me that I don't need another toy?
 
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TonyAngel said:
Cool, according to that graph, 10.5 is a sweet spot in terms of velocity and compactness.
Click to expand...

Yeah. It’s pretty much the shortest you’re going to get and probably not have any issues.

I’ve had most of the rifle and pistol lengths for the AR platform and for AR pistols I think 11.5 to 12.5 is slightly better just so long as you don’t have scads of gizmos on the front of your weapon making it muzzle heavy.

Balances well and it extends the range slightly where you’ll still get fragmentation.

I was online on PSA's website last night about to pull the trigger on a 10.5 upper that they have on sale for $150. Gunshow this weekend and was gonna grab a pistol lower. Checked my play account to see if I needed to move some money around and discovered a bunch of unauthorized charges on my card. Pfft, had to get on the phone with the bank and cancel the card. Should I take this as the universe trying to tell me that I don't need another toy?
Click to expand...
It’s fate telling you that you need to buckle down and get the best one you can. That they could possibly be more difficult to get in the future.
 
Well, my gut was to go with the 10.5 inch barrel, it looks like you guys all more or less agree. Thanks for the input!

My other idea for another build was to get a 13.7 inch barrel and get a long flash hider pinned and welded getting the barrel length over 16 inches. I guess that is the shortest barrel possible to do that with. I always thought it was the 14.5 inch barrel. I currently only have one AR, but I think I need 5 total.

1. My current 16 inch go-to gun, the jack of all trades
2. My half finished 10.5 inch pistol build for vehicle or close quarters work. (I might transition that to my main go-to gun if it turns out nice)
3. A 13.7 inch pinned/welded non SBR build
4. An 18 inch DMR/SPR type gun with an A2 stock
5. Another 16 inch beater truck gun.

And maybe a 300 Blackout pistol upper just because... America!

Now to convince my wife...
 
American_Fusilier said:
Well, my gut was to go with the 10.5 inch barrel, it looks like you guys all more or less agree. Thanks for the input!

My other idea for another build was to get a 13.7 inch barrel and get a long flash hider pinned and welded getting the barrel length over 16 inches. I guess that is the shortest barrel possible to do that with. I always thought it was the 14.5 inch barrel. I currently only have one AR, but I think I need 5 total.

1. My current 16 inch go-to gun, the jack of all trades
2. My half finished 10.5 inch pistol build for vehicle or close quarters work. (I might transition that to my main go-to gun if it turns out nice)
3. A 13.7 inch pinned/welded non SBR build
4. An 18 inch DMR/SPR type gun with an A2 stock
5. Another 16 inch beater truck gun.

And maybe a 300 Blackout pistol upper just because... America!

Now to convince my wife...
Click to expand...

If you’re putting that 13” on a pistol lower you don’t need to pin it. If you’re putting it on a rifle lower, might as well go with the 14.5 and get a muzzle device that does something.

My main rifle is a 14.5 with a pinned Levang Linear Comp. I like it.
 
American_Fusilier said:
Well, my gut was to go with the 10.5 inch barrel, it looks like you guys all more or less agree. Thanks for the input!

My other idea for another build was to get a 13.7 inch barrel and get a long flash hider pinned and welded getting the barrel length over 16 inches. I guess that is the shortest barrel possible to do that with. I always thought it was the 14.5 inch barrel. I currently only have one AR, but I think I need 5 total.

1. My current 16 inch go-to gun, the jack of all trades
2. My half finished 10.5 inch pistol build for vehicle or close quarters work. (I might transition that to my main go-to gun if it turns out nice)
3. A 13.7 inch pinned/welded non SBR build
4. An 18 inch DMR/SPR type gun with an A2 stock
5. Another 16 inch beater truck gun.

And maybe a 300 Blackout pistol upper just because... America!

Now to convince my wife...
Click to expand...

For number 3 these guys have a good 13.7” AR.

https://sonsoflibertygw.com/build-a-rifle/patrol-series-rifles/

That’s the price after a few upgrades. You can get it for less than that.

8FC07B8C-07B4-4414-A2A3-1218F98ABA7B.jpeg
50BFEA6A-3482-42A6-A35D-D33AEB01A87D.jpeg

I have one more to get (another BCM 16” MLOK with an Aimpoint T2). After that I have a few upgrades to make here and there (better light here, optic there etc), but that’s the bulk of it.
 
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Another thing to consider (beyond muzzle velocity) is engagement distance. (because one effects the other) With the shorter barrels, (and the corresponding lower MV) the weapon becomes a closer range system. I do love my handy little 10.3", and 10.5 pistols, but I consider them close in guns. I don't expect them to be effective on targets at 300 yds, and out. Oh sure I can HIT targets at that range, but the terminal ballistics that have been discussed here is effected, so unless it's a range toy, I consider these small package guns as close range defensive weapons.

I deploy them in that role.

This isn't a problem anyway in my book, as within the legal system, I'd have a devil of a time proving a defensive shoot at distance in a court of law.
 
I presume the graph is for 223/556 55gr factory load.
Does anyone have yet another pertinent tidbit of info, ft lbs of energy / barrel length?

Seems 10.5'' barrel for the win for a pistol length. At least in 223/556 caliber
 
DoubleMag said:
I presume the graph is for 223/556 55gr factory load.
Does anyone have yet another pertinent tidbit of info, ft lbs of energy / barrel length?
Click to expand...
Depends on the load really.

I use a couple of these in my shorties.

https://www.recoilweb.com/sbr-ammo-buyers-guide-141394.html
Seems 10.5'' barrel for the win for a pistol length. At least in 223/556 caliber
Click to expand...
I prefer the 11.5 or 12.5 because of the balance and the handling. I’m also getting 150 FPS extra out of some loads.

That’s nitpicking though. In short barreled weapons I’m still trying to wring every bit of velocity and ft lbs I can while still having a weapon that’s maneuverable while getting in and out of a vehicle.
 
I like my 11.5" 5.56 and I would choose that length again. Whatever length is decided upon the longest possible gas system is going to be the way to go. I have a carbine length system and still run a AGB.
 
I have a 7.5" AR pistol...and for the most part it's about as useful as boobs on a boar. It's loud, chucked massive fireballs before popping on the Smith Vortex, pretty accurate at 25 yds, so-so at 50...dumb at 100.

I really need to convert it over to 300 BLK...
 
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