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Posted: 8/1/2014 6:14:41 AM EDT
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Anyone here own both an 11.5 and 12.5?
My next ar is going to have one of those two barrel lengths. It is a sig brace pistol build. I have a bcm a4 20" with a variable power scope I use for 100-400 yards (that's the farthest I've been able to find a place to shoot). This pistol rifle firearm whatever u wanna call it wil have an aim point micro and will be my bedside/camp gun since the 20" is rather unwieldy indoors. I'm torn between that 1" difference in barrel length. I don't know if going the extra inch is worth it. I will be shooting with this gun out to 150 yards but primarily 50-100yds. What are if any the pros and cons between the two lengths? I will have this rifle loaded with soft points or otm or bonded rounds when using it for protection but will do all my plinkig with xm193 and 855 |
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1" doesn't mean as much from 11 1/2 to 12 1/2 as it does from 10 1/2 to 11 1/2. IMO the 11 1/2 is the perfect size
for a short barrelled rifle. Velocity is considerably better than 10 1/2. Going on up to 12 1/2 doesn't give you much more in terms of velocity but it does add another 1" in length. Personally I would get the 11 1/2" |
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I have both. The 12.5" is basically my primary, but prefer the 11.5s when running suppressed.
The length of my SF suppressor mounts is definitely a factor - a 12.5" with an A2 would be roughly the same length as my 11.5" with a SF 3P FH. If you plan to run yours without a can, I'd lean 12.5", 11.5" if suppressed. Once you put a 4oz mount and a 17oz can on a 12.5", it becomes much less handy. |
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I've got several, 10.3", 10.5's, 11.5's, 12.5's and my favorite is our 12.5" MID length gas. That is about as short as you can go on a Midlength gas system. I was running a 11.5" for the reasons others mentioned but went up to a 12.5" since our barrels run great with a Mid gas system. So they are smoother without a suppressor and our adjustable gas block makes it smooth with a suppressor. We are using a patented hybrid polygonal rifling which produces more backpressure than other barrels we have tested so the port sizes are smaller. I'm running the 4th barrel down in the picture below:  Here is my setup suppressed:  I put a 6-24 power scope on it and got a .65" group at 100 yards.   We are turning some fluted 12.5" Mid's now:  Here is how it runs in full auto unsuppressed and suppressed:  Some more info, pics and vid on my site: http://micromoa.com And our Facebook page: https://www.facebook.com/MicroMOA |
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Check out the first picture I posted. Notice the 10.5 carbine barrel and compare to the 12.5 Mid barrel. Dwell time is the same but pressure is less on the Mid as the port is further away from the chamber. As mentioned, we did some testing on other barrels doing the 12.5 Mid. We took a well known cold hammer forged barrel which was originally a 14.5 Mid and cut it down to 12.5 and it wouldn't be reliable till the port was .089 while our barrels run reliably at .078. At .089 it was kind of pointless as it wasn't that smooth. In contrast, most manufacturers port there 14.5 and 16" Mid barrels at around .078 - .082. |
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Quoted: Damn!! A 12.5" middy? Sign me up. When do you expect to have those fluted 12.5s ready? I was hoping they would have already left the shop for nitriding last week but we are in the middle of changing our cutter configuration. So now waiting on a different tool holder. We've done all the 16" Rifle gas ones for this run and just need the new cutter setup to complete the 12.5 Mid's to send them all out together. I'll update our Facebook page once they have left the left the shop. Hoping this week! Thanks! |
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