Sense you are shooting at a range, you can keep your advice purely on an accademic level by saying something like:
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"Oh, did I tell you? I was talking to some folks on the muzzleloading website and the folks there were saying that at the ranges they shoot at no one is allowed to pop a cap on their gun unless they are standing on the firing line with the muzzle pointed downrange!
They were also saying, any time anyone carries a rifle around at their ranges, when they are not on the firing line, the muzzle has to be pointed at the sky. No exceptions.
Sounds like pretty good advice to me! I bet the rules here are similar, or at least they should be.
One guy actually said he was glad that he was on the firing line with the gun pointed downrange when he popped a cap with his unloaded gun. Turned out that the damn thing was loaded after all! Boy, can you imagine how dumb he felt?"
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Of course, I wouldn't expect you to use my words but to use your own but you get the idea.
IMO, by keeping it impersonal it should not cause a problem with your friendship but it still lets him/her know what the rules should be and that you are in agreement with them.
zonie
PS: If he answers "Those sound like pretty good rules." you know your "home free".
If he answers "Sounds like a bunch of dumb, picky ideas that some weenie dreamed up just to pick on us shooters." you know your in for a rough row to hoe and will have to decide if you want to be around him when he's shooting a gun.