MK 12 Mod 0 300 Blackout is complete

Jeff in TX

Full Member
Sep 5, 2004
McKinney, TX
Finally got the 300 Blk Out Mk 12 Mod 0 completed. Took it out to the range this morning for the testing. Supersonic loads loads shoot .75" moa at 100 yards. The 208 gr Hornady AMAX sub sonic loads shoot a hair under 1 moa which blew my mind. Wow is it accurate with both super and sub sonic loads! This is such a fun gun to shoot though I do have one issue. I've got the adjustable gas block wide open. It ejects rounds just fine but won't cycle another round. Talked to my smith and he said he'd have to open the port a bit.

It's not an exact clone of the MK12 Mod 0 but it's about 90%

CMMG Lower with A2 stock
MK12 MOD-BLK Upper:
Oden 16.1" pistol gas block barrel
PRI Gas Buster Charging Handle
PRI Full Length Forearm
PRI MK12 MOD 0 Rail
PRI Flip up Front and Rear Sight
ARMs #22 Throw lever Scope Rings
Leupold VX-R 2-7X33 FireDot Duplex Recticle Scope
MagPul MS3 G2 QD sling
Ross Precision 30 Cal titanium Suppressor [IMG2=JSON]{"data-align":"none","data-size":"full","src":"http:\/\/\/albums\/v98\/jharmon23\/AR5.jpg"}[/IMG2]


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Full Member
Feb 19, 2012
Salt Lake City, UT
Awesome looking build, man. Congratulations. Sounds like you've got a shooter. I need to research the can you've got on it; not familiar with Ross Precision.