10.5" vs 11.5" Barrels

[KevinB]

The 11.5 pressure spike for extraction is not nearly as bad as the 10" guns, so all else being equal the should be more reliable. The added barrel length is a factor for both bullet velocity and the mounting of suppressors.
Plus with the KAC URX with an 11.5 you can have a can and a GL at the same time.

[parishioner]

I vastly prefer the 11.5" barrel to the 10.5

C4IGrant with KAC SR16E3CQB

Is that the KAC T-1 mount?

[KevinB]

Is that the KAC T-1 mount?

Yes it is. However we still have not got it into production.

[krgwag]

Does anybody have the details on the costa version? I'm in the SBR planning stage now.

[KevinB]

See the KAC forum here -- we are selling the 'Block III' SBR now.

[Eurodriver]

See the KAC forum here -- we are selling the 'Block III' SBR now.

I checked. I didn't see anything.

[fdxpilot]

a 10.5 with a 5.5 inch flash suppressor welded on is the worst of all worlds.

You get the velocity of a 10.5" without the additional muzzle velocity and stability of a 16" bbl.

Its a pointless combination. Either wait until you have the extra $200 to SBR it, or just get a 16" bbl.

Don

I agree. All the downsides of a longer barrel with none of the advantages. The only good thing about a short barrel is size. If you give that up with a long pinned flash-hider, what use is it.

[devinsdad]

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

[polydeuces]

I was told by "someone" that the ideal length is 12", or as close to it as possible.
This being the length giving the best combination of performance/size, which exhaustive tests (on our tax-dollars) apparently have shown.

Won't name this person, because it is not my place to do so, but rest assured his opinion is highly regarded across this board.

Having an 11.5" SBR puts me close, but I am seriously looking at getting a Centurion barrel and have it chopped to just that, not that it shoots bad now - far from it but for no other reason than silencing my inner OCD child....

[Ironman8]

I was told by "someone" that the ideal length is 12", or as close to it as possible.
This being the length giving the best combination of performance/size, which exhaustive tests (on our tax-dollars) apparently have shown.

Won't name this person, because it is not my place to do so, but rest assured his opinion is highly regarded across this board.

Having an 11.5" SBR puts me close, but I am seriously looking at getting a Centurion barrel and have it chopped to just that, not that it shoots bad now - far from it but for no other reason than silencing my inner OCD child....

I know you're trying to be vague about "who" told you this, but what in particular would a 12" do that a 11.5", 12.5", or even 14.5" can't? What could possibly be the benefits to the system with a change so small?

BTW, not being confrontational, actually very curious since I may chop a barrel down for use with a suppressor (trying to get the Ops Inc line of suppressors to mount just about right to the rail of a 9" VIS....which just so happens to require right about a 12" barrel )