Challenge them
We used to take a T/C to the local range. We had .410/.45Colt, .30-30, .30-06 (ouch) and .270 (again, ouch) barrels for the gun. We had the guys out there saying "Oh, that's not a pistol! That's a rifle!" that swore up and down they could shoot their pistols better than we could. We'd simply ask them how well they could shoot their rifles. "Oh, we're the best riflesmen in the world!" Yeah, okay. My uncle would them pull out the cannon (.30-06) and say "Fine, if you're such a great riflesman, then how about a competition. Your rifle against my pistol at 200 yards. Three shot group. Closest to bullseye and tightest group." "You're on! What are the stakes?" "Guns." You'd be surprised how many rifles we'd turn over to the county sheriff after telling him "Well, this might get reported stolen..."