SBR 556
- Thread starter prairiefire
- Start date
I've been deliriously happy with my BCM 12.5 upper. Haven't shot it past 300, but out that far it appears to work like a 16" gun. Seen a bunch of smart folks tend to agree that it's the sweet spot, and also that under about 10.5-11 is starting to get to troublesome areas.
Even at 12.5 you loose enough velocity the max range at which terminal ballistics are as-designed drops off noticably; below that speed you just punch .22 holes in them. If you expect to have to shoot far away (also vehicle defense, your home has acreage instead of a yard) so there's a chance you need to stop at 3-400 yards, then look for quality ammo optimized for short barrels; it will have bullets which will perform well with the reduced velocity so you can sidestep the issue. If home defense = indoor ranges, the bullet is moving right along at muzzle who who cares?
It can get as complex as you wish also. Say you want to plan on shooting people behind barriers (or, through soft armor)? Your best bet in barrier blind ammo can still drop up to 400 fps just getting through it. Out of a 10.5" gun, that could put you below the terminal performance threshold at point blank ranges. With a 12 or 14" gun, you have enough velocity to take barrier shots out to as much as a couple hundred yards.
I also have a 10.5" .300 and think by the time you get down there it begins to be tight on handguard space for a normal grip, and accessories if you are that kind of person. Even if ballistics and blast were not an issue, a pistol length gun (e.g. 7") would have to be run totally differently, with a dedicated VFG, say.
Even at 12.5 you loose enough velocity the max range at which terminal ballistics are as-designed drops off noticably; below that speed you just punch .22 holes in them. If you expect to have to shoot far away (also vehicle defense, your home has acreage instead of a yard) so there's a chance you need to stop at 3-400 yards, then look for quality ammo optimized for short barrels; it will have bullets which will perform well with the reduced velocity so you can sidestep the issue. If home defense = indoor ranges, the bullet is moving right along at muzzle who who cares?
It can get as complex as you wish also. Say you want to plan on shooting people behind barriers (or, through soft armor)? Your best bet in barrier blind ammo can still drop up to 400 fps just getting through it. Out of a 10.5" gun, that could put you below the terminal performance threshold at point blank ranges. With a 12 or 14" gun, you have enough velocity to take barrier shots out to as much as a couple hundred yards.
I also have a 10.5" .300 and think by the time you get down there it begins to be tight on handguard space for a normal grip, and accessories if you are that kind of person. Even if ballistics and blast were not an issue, a pistol length gun (e.g. 7") would have to be run totally differently, with a dedicated VFG, say.
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Most research suggests the 11.5” is the optimal with a carbine gas system. Great cycling and still short. 12.5” and 14.5” work nicely, too, but steer to lose their shortness
For 5.56, I like 12.5" barrels. I have had 10.3", 11.5", 12.5" and 13.5" . Sold off the the 10.3" and 11.5" because I didn't feel like they provided enough of a difference with shorter length compared to the 12.5". I run the 13.5" in 2-gun competitions for a little extra velocity over the 12.5", if needed. For me, the 12.5" barrels are long enough to get decent velocity from all of the ammo that I use in almost all situations. You can run a full-size can on them without it feeling overly long and a mini can isn't overly blasty or obnoxious. I run muzzle brakes on most of rifles and 12.5" didn't seem to hammer my range neighbors quite as much as the shorter lengths the few times I didn't have the gun suppressed.
