i have a gemtech multimount 9mm can that i put on my glock and my AR in 9mm. i dont use it as much as i thought i would, partly because of the ballistics of a 9mm. i know gemtech says you shouldnt run most other calibers through it, but my guess is that a 300 whisper is probably about the same pressures as a 9mm non subsonic. i dont have any 300 whisper data to look at in comparison so i am asking here. has anyone done what i am talking about?