As far as an actual tactic I’ve employed both muzzle strikes and my personal favorite a hockey style cross check with my hands on the fore rail and receiver extension of an M-4 to people who didn’t want to get with the program. I’m not a small dude and the cross check has not yet failed to put someone down. This was in a On Duty setting and I had other lethal and non-lethal options available to me in case the subject attempted to take the rifle. I’ve also been in a number of fights with a slung rifle and it’s awkward to say the least (pro tip: a rubber bumper on your stock may be a good idea, I’ve had the rear edge of a standard M-4 stocks open up my face a couple times pretty bad while grappling).