IF I ever have an issue with ANY member of a group, be it the gun owner or otherwise, I simply point out to them that before things escalate, the ONLY loser is going to be the one with a SGC. He is the one who will then tell his mates to shut up and leave. A slightly different scenario, I know, but on one occasion I suspected that a team of 'cowboys' who shot up to our game shoot boundary, were coming onto 'our' side after we were beating a wood away from the boundary. I gave my gun to one of the beaters to carry and I stayed behind in the edge of the wood. Sure enough 6 guys with guns came through the gate and lined out on our land.. I let them fire the first few shots and then emerged and confronted them. Transpired that of the 6, only 2 had SGC's. They were a bit "well, what are you going to do about it then " ? I simply pointed out that armed trespass carries a power of arrest and that I was quite prepared to spend the remainder of the day at the local nick, if they wished. They backed off and we never had any further problems. Or, as already said, at least tell the shoot organisers. Having run a shooting ground I know just how difficult it is to 'see' everywhere and I relied a lot on other people bringing things to my attention.