Thought I had this all figured out, but NOOOOOO, I gotta keep reading. BCM vs. Faxon vs. flow guys vs dwell guys. My head hurts.

In my effort to select a barrel length for an AR pistol, I just want some real-world data comparing apples to apples. I will mostly be shooting 55 gr XM193, but I'll gladly accept ANY chrono data out of the two lengths listed. Thanks.

FPS aside, it seems the 10.5 length is far more finicky than 11.5. I was contemplating the same thing last year and went 11.5, not based on velocity, more from a reliabilty standpoint.

Same as Warpig, 11.5” BCM for me.

From an old (August 2014) post. Not exactly what you want, but possibly of some value.

________________________

Colt LE6920 AR-15 for the 16 inch barrel benchmark, and a friend supplied three home-built ARs with 18 inch, 11.5 inch, and 7.5 inch barrels. He also provided a Thunder Beast 223P-2 suppressor for use on the 11.5 inch barrel. Ammunition was Lake City M193 55 grain full metal jacket 5.56mm NATO and Speer 223 Remington Gold Dot 64 grain soft point. All barrels were fouled with three shots before recording began. Each trial con-sisted of 10 shots.
Chronograph was an Oehler 35P whose start screen was placed 10 feet from the rifle muzzles.

Average instrument velocities and energy.

M193 55 grain FMJ

18": 3152 feet per second / 1193 ft-lb
16": 3039 fps / 1128 ft-lb
11.5": 2752 fps / 925 ft-lb
11.5" with suppressor: 2786 fps / 948 ft-lb
7.5": 2234 fps / 609 ft-lb

Gold Dot 64 grain soft point

16": 2769 fps / 1090 ft-lb
11.5": 2507 fps / 893 ft-lb
7.5": 2007 fps / 572 ft-lb

What surprised me was the dramatic and seemingly disproportionate velocity losses in the 4 inches from the 11.5 to the 7.5 inch barrels. I also found the velocity increase as a result of using the suppressor to be interesting. I’d read that it sometimes occurs, but I was always a little skeptical of the claim until today.

I put a 10.5" Faxon & a 10.3" Daniel Defense barrels on x2 separate uppers.

I've had zero issues with either. I've ran everything from 55-77gn through them. I've heard of people having reliability problems. I've just never experienced any with shorter barrels.

quote:

Originally posted by WARPIG602:
FPS aside, it seems the 10.5 length is far more finicky than 11.5. I was contemplating the same thing last year and went 11.5, not based on velocity, more from a reliabilty standpoint.

I've noticed the 11.5 run better in full auto as well,

but if you install a 3rnd burst , it doesn't seem to make a diff between 10.5 and 11.5

Thank you gentleman. Who's running an adjustable gas block?

quote:

Originally posted by Chris Orndorff:
Thank you gentleman. Who's running an adjustable gas block?

I've got an Syrac Adj Gas block on my 10.5" SBR with a T2 buffer. Never had any issues with it. Just happen to be the buffer that came with the spikes buffer tube.

quote:

Originally posted by Chris Orndorff:
Thank you gentleman. Who's running an adjustable gas block?

I am as well but on my 14.5. I've never had any issues with it but something won't let me put one on a gun Id consider for serious defensive use. Probably just my squirrel brain at work.

I have an El Cheapo 10.5" PSA build. It has not had a single hiccup in 5000 rounds.

And I would prefer not to have to run an adj gb as well.

Ryan, do you run yours suppressed?

I have a 10.3" and an 11.5"
Caveat is that the 10.3" is a DD barrel, so the gas port is slightly larger to compensate for the shorter dwell time.
They've both been 100% flawless. No adjustable gas blocks, shoot both suppressed and unsuppressed. Ammo has primarily been 855, 193, 55gn federal 100 round packs.
I think the 10.3 is my favorite of the two. Not real sure yet, though. overall length is the same, though since I added the Law Tactical folding stock adapter to the shorter of the two.

quote:

Originally posted by Ryanp225:
I have an El Cheapo 10.5" PSA build. It has not had a single hiccup in 5000 rounds.

While not saying PSA isnt capable of producing quality guns. I've found round count as a measurement of quality or reliability to be somewhat arguable. I typically say the same of any gun, if youre gun has never had a hiccup, you phavent run it hard enough. 5k rounds of 100 a week with a cleaning in between is different than 5k in week. Not saying you're wrong or incorrect. Many members here have been quite happy with their shot barreled PSA uppers.

quote:

do you run yours suppressed?

If it matters my 10.5" runs fine with & without the can. I notice little difference except for noise & little extra smoke from back pressure. But I only really notice that indoors.

quote:

Originally posted by WARPIG602:

quote:

Originally posted by Ryanp225:
I have an El Cheapo 10.5" PSA build. It has not had a single hiccup in 5000 rounds.

I typically say the same of any gun, if youre gun has never had a hiccup, you phavent run it hard enough.

So you are saying if I don't abuse my guns until the point of failure I'm "not doing it right"?
Good luck there buddy.
I haven't blown up the engine in my car either. Am I not driving hard enough?

This message has been edited. Last edited by: Ryanp225,

quote:

Originally posted by Chris Orndorff:
And I would prefer not to have to run an adj gb as well.

Ryan, do you run yours suppressed?

No, I don't use suppressors.

Its late and I am on my phone but my velocity number s for my 11.5" agree with what has been posted. I use a AAC 7.62 with no issues. I think it has a T2 buffer.

With M193 the velocity is borderline as I believe 2700 is the floor for the round to "tumble" but with 55gr TsX or GD the floor for expansion is around 1700.....that gives it a range of around 225m.

You should see an increase of 100 to 150 fps going from 10.5 to 11.5".... thats the reason I switched.

No functional issues to report in several thousands rounds.....just a nose full of gas when suppressed

quote:

Originally posted by Ryanp225:

quote:

Originally posted by WARPIG602:

quote:

Originally posted by Ryanp225:
I have an El Cheapo 10.5" PSA build. It has not had a single hiccup in 5000 rounds.

I typically say the same of any gun, if youre gun has never had a hiccup, you phavent run it hard enough.

So you are saying if I don't abuse my guns until the point of failure I'm "not doing it right"?
Good luck there buddy.
I haven't blown up the engine in my car either. Am I not driving hard enough?

I never said that. You put that in quotes. I was simply saying that rounds fired isnt always an accurate determination of reliability.

quote:

Originally posted by WARPIG602:

quote:

Originally posted by Ryanp225:

quote:

Originally posted by WARPIG602:

quote:

Originally posted by Ryanp225:
I have an El Cheapo 10.5" PSA build. It has not had a single hiccup in 5000 rounds.

I typically say the same of any gun, if youre gun has never had a hiccup, you phavent run it hard enough.

So you are saying if I don't abuse my guns until the point of failure I'm "not doing it right"?
Good luck there buddy.
I haven't blown up the engine in my car either. Am I not driving hard enough?

I never said that. You put that in quotes. I was simply saying that rounds fired isnt always an accurate determination of reliability.

It's what you implied.
I think I get what you are saying and I agree that it's not the final word in reliability but for all of us who are not so high speed and don't use our rifles daily in a war zone I think it's good enough wouldn't ya say?