Best barrel length for 5.56 SBR

[tacticalmaster45]

11.5" BCM - feels perfect

 

[roscott]

I've got a 11.5" BCM barrel on my AR pistol. While dwell time can be an advantage for cycling and not damaging cans, as many have said, there are plenty of good shorter AR's out there.

What you give up is velocity, and that's important if you plan to shoot anything besides paper. When I was researching lengths, I found that 5.56 is really only an effective combat round because it tumbles, and it only tumbles over a certain velocity. Slow it down enough, and you lose effective "tumble-range." Slow it down enough, and it won't tumble even at hallway distances. I don't recall the exact numbers of "x barrel will keep y speed until z distance," but IIRC you really start losing under 11".

 

[avboiler11]

Civilians aren't bound by Hague restrictions on expanding bullets.

 

[roscott]

Civilians aren't bound by Hague restrictions on expanding bullets.

True. I suppose I should have added if you want to use bulk or military ammo, rather than SP or HP.

 

[avboiler11]

Indeed.

Many people shooting SBRs are concerned about max effective fragmentation range for M193, M855, or even Mk262...when the reality is modern expanding bullets allow impressive terminal effects at substantially lower velocities than FMJ or OTM bullets, making max effective range much further than what a 'warfighter' might be limited to.

 

[cop car]

IMO there is nothing wrong with setting up your rifle for the most common ammo found. there is also nothing wrong with setting up a rifle for a specialized purpose. Rifles are packages. Ammo, barrel length and twist, optics and the rifle as a whole have to be planned out together.

Indeed.

Many people shooting SBRs are concerned about max effective fragmentation range for M193, M855, or even Mk262...when the reality is modern expanding bullets allow impressive terminal effects at substantially lower velocities than FMJ or OTM bullets, making max effective range much further than what a 'warfighter' might be limited to.

 

[ljk]

MK18 is 10.3", all 4 of my SBR are 10.5", never had any problem with it.

BCM says 11.5", well the are not on the MK18 contract like DD, LMT, etc.