SBR Barrel Length

Reptile

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10.5 because I heard shorter does not run well.

If I wanted longer I'd get 14.5 but for that you can put a brake on it without nfa.

If you want to see some great 10.5's look at noveske.
 
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Here's some info to help you decide:

Q: Why BCM chose the 11.5" SBR over the 10.5"

I get this question a lot. It is a good one. When we spec our program we can build anything we would like, so we sat down and looked at the pros and cons.

First Statement: I know a good 10.5" SBR can run very well. I personally own a semi MK18 type and it runs great. No problems.

A: Dwell time.
Dwell time is the time that your gas operated weapon maintains pressure to continue the cycling of the weapon. It primarily exsists from the time the bullet passes the gas port in the barrel to the time the bullet exits the muzzle. When you pull the trigger and fire the weapon the movement of the bolt carrier group unlocks the bolt, extracts, and ejects the spent casing. Then it cocks the weapon, feeds, chambers the next round, and then locks again. One of the thing that can make SBRs finicky is the dwell time (or lack of).

The 11.5" carbine is approximately 4% longer weapon than its' 10.5" counterpart, but this extra inch gives the barrel a 40% increase in length for dwell time. IMHO, this is an excellent trade off. This additional dwell time (all other things being equal) will allow the carbine to be more forgiving to different ammo types, extremes in air temperature, weak or worn extractor springs, worn extractors, buffer weights, etc.

Last Statement: For those folks who have a 10.5" that works very well, I would reply; me too. (see first statement)

If I had to "go to war" with a AR15 Carbine, I would grab the BCM 11.5".
The BCM 11.5" Runs Like a Dream.

Hope this info helps,
Paul
 
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Here's some info to help you decide:



this is great info.

i've only had problems with my 10.5" a small number of times. with the can on there and increasing what are already high pressures that is usually when i've had issues. though i think frenchman managed to frighten the blaster into choking on its own food really bad once. [laugh]
 
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I ended up going to 300blk in 8.5"because I wanted short.and as minimal concussion possible. Put a linear comp (simple threaded device) to further alleviate blast.

Need to get it engraved before I can fully assemble and shoot it.
 
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I went with 10.5". I thought about going to a 7.5", but read there were a lot more problems with that short of a barrel. I also was going the inexpensive route, and the company I bought from (MAS Defense) only had 10.5" and 7.5" for pistol/ SBR's barrels. Works great!
 
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I was initially thinking 9mm for that same reason
Speaking of non-NFA 9mm ARs, Palmetto has started to offer a "pistol kit" to build out any stripped AR lower into a 10.5" free-state-legal 9mm pistol:

I'm hoping they start selling the AR-9 shorty uppers by themselves, I don't need the rest of the kit.
10.5 because I heard shorter does not run well...If you want to see some great 10.5's look at noveske.
I wouldn't go shorter than 10.5 on a .223 if only because it pretty much becomes a machine for emitting fireballs rather than bullets with an effective velocity.

And I agree on Noveske (the one on the bottom, the top gun is a different project entirely);
 
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I went 10.5 on my piston build because that's what HK did with the 416. because HK.
 

edmorseiii

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I slapped a 7.5" 5.56 pistol together after I moved with bargain shopping parts, because NH. It runs fine, but it is a toy. For 5.56, I wouldn't go any shorter then 10.3" if you had any intention of using it as a rifle.

My 300blk runs awesome at 8.5", and the 9mm I intend to slap together when I get a pistol can will likely be a 5" barrel, but with 9mm you don't have to worry about a gas system.
 
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Did a 7.5 build for 5.56. Is it useless? Yes... is it fun? Hells yes...

I'm not worried about using it to defend the motherland so it's just a fun thing...

Sent from my KFSOWI using Tapatalk
 

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Did a 7.5 build also, it is fun to shoot and the muzzle blast is coolimage.jpg
Here is a picture.
 

warwickben

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What would you run for a 9mm and 45.
I'm leaning towards 10.5/11.5 for 5.56 . It's not for a ar, but with the way it's going to be made the over all length wouldn't change if I used a shorter then 10.5 barrel .
But I know with some pistol rounds you lose velocity etch after a shorter length . But looking a Baltic data confuses the hell out of me.
 
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Awesome info here. I was initially thinking about going 8.5, but after reading some of this I think for my 5.56 build, I'll stick with the 10.5, and pair a 12" Seekins BAR with either a Ferfrans or Noveske KX5.... I'm also gonna need a barrel... Details.
 
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edmorseiii

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What would you run for a 9mm and 45.
As short as you want, there is no gas system to worry about. I am looking at 5" for my 9mm because I am eyeballing a TiRant 9 which is ~8" long, so I can tuck it all under a ~10" float tube of some sort and look boss.
 
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I went 10.5 with my 5.56. Didn't see the bcm article at the time, but I'm still happy with my choice. For 9mm I'm considering 5" with a vfg, but question how it will look/ handle. Maybe 7" is better?
 

warwickben

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As short as you want, there is no gas system to worry about. I am looking at 5" for my 9mm because I am eyeballing a TiRant 9 which is ~8" long, so I can tuck it all under a ~10" float tube of some sort and look boss.
The 45 will be gas , less recoil and don't need a 1.5 to 2 pound bolt . But gas blot is tight next to the barrel nut. If I move to a free state or get my shop rezoned so I can apply for a FFl I could run a can and have it the same length as the 5.56 barrel .
 

ScottS

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I have two 10.5" 5.56's, and they both run like sewing machines. I figured good enough for Crane (Mk18), good enough for me.

In fact, I like 10.5" so much, 16" AR's start to feel like jousting lances now.

ETA: Open invitation if you're in the area to try one out so you can judge the feel for yourself. I live less than 4 miles/10 min from the range.
 
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BadBoyBilly

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I was going to go with a 7.5" but I've read a lot of info about them having issues. Going with a 10.5" Carbine gas system for the extra reliability.
 
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I was going to go with a 7.5" but I've read a lot of info about them having issues. Going with a 10.5" Carbine gas system for the extra reliability.
Haven't had any problems with mine, but I don't run that many rounds through it. It's just a fun toy to make people at the range stop and look

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Is there anything special I should consider before assembling a 9mm upper, e.g. headspace for the chamber? I know I want a ramped bolt, and captive Colt 9mm magazine adapter. I already have a pistol lower with matched upper.

I went 10.5 with my 5.56. Didn't see the bcm article at the time, but I'm still happy with my choice. For 9mm I'm considering 5" with a vfg, but question how it will look/ handle. Maybe 7" is better?
For 9mm with a suppressor, seems like a lot of people go as short as 4.5", micro-uzi style.

As short as you want, there is no gas system to worry about. I am looking at 5" for my 9mm because I am eyeballing a TiRant 9 which is ~8" long, so I can tuck it all under a ~10" float tube of some sort and look boss.
That's my current thought, but I'd go with a shorter rail, just because I prefer a half inch or so of the suppressor extend out, like so:
 
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Riddle me this...

So, I'm waiting on my stamp approval... You know, again... And I'm wondering, can I buy the barrel before the stamp gets approved, or should I wait it out. My gut feeling is to play it safe and wait to get the stamp back. What say you?
 

ScottS

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So, I'm waiting on my stamp approval... You know, again... And I'm wondering, can I buy the barrel before the stamp gets approved, or should I wait it out. My gut feeling is to play it safe and wait to get the stamp back. What say you?
Buy a pistol buffer tube (cheap), and then buy the barrel and build the weapon up as a pistol. Shoot the shit out of it waiting for the stamp. When the stamp comes in, pull the pistol buffer and replace with a stock.

Easy-peasy, and you can confirm the gun runs, you don't have to worry about missing out on a barrel sale, etc.
 

dcmdon

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So, I'm waiting on my stamp approval... You know, again... And I'm wondering, can I buy the barrel before the stamp gets approved, or should I wait it out. My gut feeling is to play it safe and wait to get the stamp back. What say you?
Just buy the barrel now if you want to. As others have shown, the idea of constrictive intent also leads to a pistol build.

Its also not diabolical. Its simply exercising your rights within the letter of the law. People need to stop being afraid to exercise their rights WITHIN but up to the edges of the law. Its this endemic worrying mentality among MA people that drives me nuts.
 
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