Gas port hole size for 7mm-08 AR with 18" barrel and Rifle Length Gas System??

[Vette447]

I am working on a custom MATEN MKM build and I am building it as a "lightweight" hunting rig with an 18" barrel in 7mm-08. Does anyone know what would be the optimum gas port hole size for this setup? I know I remember reading about someone that built an 18" (.308 I believe) with the rifle length gas system and they were initially having trouble with it not cycling until they increased the gas port hole size. I am also looking to use the JP Low Mass bolt carrier with adjustable gas block.

I am hoping the one of the experts here may have built something similar and could help me out with some knowledge learned. Thanks in advance!

 

[Jumper]

I built a 7-08 AR with a 22" bbl on a Mega MATEN platform with the JP Lo-Mass BCG. I had the upper chambered and assembled by Mark Hunt of Dicks Gun Repair in Winston Salem NC. Unfortunately I dont know the size gas port he drilled but he sized it to operate with 139gr bullets. I wanted to shoot 162gr. Between the heavier bullet and the lightened BCG, it was over gassed and I had to throttle it back with an adjustable gas block. You could call Mark and ask: (336) 769-2939 (from the web, its probably correct. I misplaced his number). I suggest you start small with the port size.