yes, i called and that was the technical advice i was given. "and since there is no industry standard for those types( assuming he meant ar10) you may make fitment adjustments." no biggie, it's in, dry functions, took off appr .060" which i thought was a lot but i was able to get it done without harming the jay hook. i can't find cold blue, but several alternatives on brownells. after all this, i am getting itchy to build, thank you guys :o, as i removed and installed the trigger group and safety…. at least 15 times. it will be a while and a .556 gun, i don't have one, and i'm looking at larue's stealth set. and i will probably use a geiselle trigger, without hesitation, because really like their feel.