Re: SBR Preferences ?
A 10.5" will be reliable <span style="font-weight: bold">if it's built correctly</span> but generally will be harder on parts. I would get 1/7 or 1/8 twist barrel in a 10.5" if you wanted the most compact overall length, 12.5" for good terminal performance further out with most ammo, or an 11.5" for a compromise between the two. There is ammo out now that don't rely on fragmentation so take that FWIW.
I went with the Centurion Arms 12.5" barrel because of the accuracy reputation (I've had 3 barrels from Monty so far) and I think the length would be more popular if a stamp wasn't needed. When people think of getting an SBR, they usually want it to be worthwhile (meaning go as short as you can) but since it's not permanent I can switch to a different length any time if I wanted to.
Other good barrel choices are usual suspects such as Colt, Daniel Defense, BCM, LMT and Noveske.
I haven't read of any subsonic ammo that will cycle an AR or shoot worth a damn.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BravoCompanyUSA</div><div class="ubbcode-body">
<span style="font-weight: bold">Q: Why BCM chose the 11.5" SBR over the 10.5" </span>
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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