Big Frame AR question

Feb 15, 2017
My big gas gun is a KAC pattern and I understand it is one of three common patterns; the other two being DPMS and Armalite. I know there are different mags and upper/lower dimensions. What is the difference (if any) in barrel extensions and gas tubes between DPMS and KAC? I am asking because I won a certificate for a CRA/BHW barrel at the last match and they only do DPMS pattern and is like to build a second upper in 6.5 Creed.


Artillery Major
Feb 19, 2017
I have a few big cal AR guns, and I build KAC military guns as a hobby, like the Mk11 and M110. KAC has a lot of differences. But, the gas tube should be standard. Techically, KAC uses a DPMS pattern, but you will need to remove the extension and match your bolt to the barrel in head-spacing, and then the extension needs to be ground-down. A standard DPMS barrel extension is too big.

Bottom line, if you want to re barrel your SR25, you can, but it will need some gun smith time, and by someone who is a KAC armorer or is very familiar with KAC guns.