Your favorite SBR length

[outrider58]

For performance I think a 12.5” SBR is hard to beat. From a good barrel, the velocity is often within 100 FPS of a 14.5” barrel. If you’re willing to use specialty ammunition, a suppressed 10.5” barrel is hard to beat. 11.5” is a good compromise length.

As far as the whole OAL thing, I think people need to calm down. Unless things have changed in the past few weeks, the OAL measurements have not changed for SBRs. HOWEVER, The ATF has been measuring braced AR firearms with the brace taken off, or even only to the end of the receiver depending on firearm design (AKs get measured to the end of the receiver, as would Sig MPX/MCX, etc) At the moment, they do not include nonfunctional parts that are not permanently attached in their measurements. This really only matters if you want to put a VFG on a braced pistol and need 26”+ in OAL so you’re not creating an illegal AOW.

This^^^

 

[teratos]

If you’re willing to use specialty ammunition, a suppressed 10.5” barrel is hard to beat.

Curious about the “specialty ammo” remark. My 10.5 shorties cycle everything I throw at them just fine running suppressed. Am I missing something?

 

[woodline]

Curious about the “specialty ammo” remark. My 10.5 shorties cycle everything I throw at them just fine running suppressed. Am I missing something?

Terminal effects, possibly. You’d need to chronograph what your 10.5” is getting to see if you’re above reliable fragmentation threshold for M193 and other common plinking ammo. I mean it’ll probably still tumble and is better than a mean comment, but the explosive fragmentation is quite possibly going to be missing.

As far as reliably cycling plinking ammo, it sounds like you aren’t missing anything.

(Sorry, my original comment was intended to address a 10.5” for Home Defense purposes. I knew what I was talking about . . . in my head)

 

[teratos]

Terminal effects, possibly. You’d need to chronograph what your 10.5” is getting to see if you’re above reliable fragmentation threshold for M193 and other common plinking ammo. I mean it’ll probably still tumble and is better than a mean comment, but the explosive fragmentation is quite possibly going to be missing.

As far as reliably cycling plinking ammo, it sounds like you aren’t missing anything.

(Sorry, my original comment was intended to address a 10.5” for Home Defense purposes. I knew what I was talking about . . . in my head)

Good idea on the chrono. I’ll need to do that. I use Hornady Ballistic Tip for HD (that I load), as a suppressed 10.5” barreled AR is my HD gun.

 

[outrider58]

Terminal effects, possibly. You’d need to chronograph what your 10.5” is getting to see if you’re above reliable fragmentation threshold for M193 and other common plinking ammo. I mean it’ll probably still tumble and is better than a mean comment, but the explosive fragmentation is quite possibly going to be missing.

As far as reliably cycling plinking ammo, it sounds like you aren’t missing anything.

(Sorry, my original comment was intended to address a 10.5” for Home Defense purposes. I knew what I was talking about . . . in my head)

Was going to post on this earlier, but waited. Terminal effects and functionality are two different things.
From a guy who heart shoots deer with a sharp stick, terminal effects have more importance when shooting minute of man. Functionality is being able to hit where you aim your weapon. They all have their place, but function is all one needs to hit one's target efficiently. As long as your gun can do that, terminal effect becomes second place.
I'm not so concerned with velocity at that point. Just whether I can place a fatal shot efficiently.

 

[woodline]

Good idea on the chrono. I’ll need to do that. I use Hornady Ballistic Tip for HD (that I load), as a suppressed 10.5” barreled AR is my HD gun.

Looks like we run similar setups. I lucked into 300 rounds of 62gr Federal Trophy Bonded Bear Claw (XM556SBCT3) for relatively cheap awhile ago, so that’s my HD load. Before that it was Black Hills 50gr TSX. Also a great load, but painfully expensive.

Part of my interest in building a suppressed 12.5” is to get better velocities from m193. That way I’m not as dependent on specialty ammo for something like a truck gun.

 

[Squaregrouper]

I was able to get an 8.5" barrelled .300AAC to 29.2".
There is a thread somewhere in here where I explained what I did- with pictures. I'm not going to try to dig it up.

 

[woodline]

Was going to post on this earlier, but waited. Terminal effects and functionality are two different things.
From a guy who heart shoots deer with a sharp stick, terminal effects have more importance when shooting minute of man. Functionality is being able to hit where you aim your weapon. They all have their place, but function is all one needs to hit one's target efficiently. As long as your gun can do that, terminal effect becomes second place.
I'm not so concerned with velocity at that point. Just whether I can place a fatal shot efficiently.

I don’t disagree. Lone caveat is that slower .223/5.56 is more liable to overpenetrate. Matters more to me than the deer, I expect.

 

[grimnar15]

I like 10.5-11.5’ish barrels.

Damn Doc, we like a lot of the same things!

 

[teratos]

Damn Doc, we like a lot of the same things!

It certainly seems so! Separated at birth?

 

[calicojack]

No. I have 10.5” barrels on 3 and they meet OAL requirements. Remember, measure with the stock fully extended. Some stocks get you there, some won’t.

And correct me if I am wrong, but for the purposes of the Maryland OAL determination, you measure stock fully open but only to the end of the barrel thread unless the flash hider is permanently attached, correct?

 

[outrider58]

And correct me if I am wrong, but for the purposes of the Maryland OAL determination, you measure stock fully open but only to the end of the barrel thread unless the flash hider is permanently attached, correct?

Exactly
Barrel length has no requirement in SBR s in Md. Only OAL.

 

[calicojack]

I have a 10.5, a 12.5, and a 14.5. In hindsight I wish I had not done 10.5 for 5.56; but I put a lot into that upper and really don't want to change it. Agree with other comments that anything below 12.5" starts to cut into the velocity numbers. I actually think 14.5" is the best esp. for Merryland. No HBAR required.

 

[teratos]

Exactly
Barrel length has no requirement in SBR s in Md. Only OAL.

Yep. Do a VLTOR A5 buffer system and you are suddenly able to shorten your barrel a bit more.

 

[outrider58]

Yep. Do a VLTOR A5 buffer system and you are suddenly able to shorten your barrel a bit more.

Yep.

 

[outrider58]

I have a 10.5, a 12.5, and a 14.5. In hindsight I wish I had not done 10.5 for 5.56; but I put a lot into that upper and really don't want to change it. Agree with other comments that anything below 12.5" starts to cut into the velocity numbers. I actually think 14.5" is the best esp. for Merryland. No HBAR required.

SBRs are short range weapons. Bullet placement is more important than shock value. Don't worry about over penetration. If you are, maybe choose a different weapon.

 

[erwos]

• 5.56: 11.5". I have 5.56 SBRs with 13" 11.5", 10", 9", and 8.25" barrels, and 11.5" is a nice in between that doesn't kill you with concussion and maintains reasonable reliability.
• .300AAC: 8".
• .22lr: < 5" so everything stays subsonic.
• 6.5 Grendel: 12.5". You do want to retain a little more velocity with this caliber.
• 458 SOCOM: If you're shooting subs, 9.5". Otherwise, don't bother with an SBR.
• 9mm: this is a tricky one, because it depends on what you're trying to do. Pretty much anything will work. If you want more velocity, I'd recommend the 10-12.5" range. If you want less velocity - popular in competition PCC - I've seen barrels as short as 4.5". Some competition guys are even using the Taccom ULW barrels, which are basically a 5.5" barrel with a pin and weld unrifled extension to get it to 16".

 

[calicojack]

SBRs are short range weapons. Bullet placement is more important than shock value. Don't worry about over penetration. If you are, maybe choose a different weapon.

I get your first two points; makes sense. Not sure where over penetration is an issue with a shorter barrel (?) Or are you saying I do not have to worry about over penetration with a shorter barrel?

 

[teratos]

I get your first two points; makes sense. Not sure where over penetration is an issue with a shorter barrel (?) Or are you saying I do not have to worry about over penetration with a shorter barrel?

The slower the projectile goes, the more problems you will have with over-penetration. With M193 ammo, the projectile is moving so fast, it fragments easily when hitting a barrier because of the energy it carries. Same effect as jumping of a diving board vs jumping off the Golden Gate Bridge. Believe it or not, slower projectiles like pistol rounds, buckshot etc. are much more likely to go through multiple sheets of drywall.

Shorter barrel, less velocity.

 

[calicojack]

Yep. Do a VLTOR A5 buffer system and you are suddenly able to shorten your barrel a bit more.

The MAGPUL ACS and ACS-L also have a longer max LOP; 14.9"