Just tell the guide the bullets ARE 180's. This little white lie will prevent any silly arguments.
I have found many guides to be pretty mule-headed in their "knowledge," partly I'd guess because they consider themsevles experts in all things related to hunting. They may be great at finding game, but this doesn't mean they know much about rifles, ammo, scopes. etc.
A good example is that I am very comfortable using 6x scopes in thick cover, in fact prefer 6x because I can often see the target better than with traditional "woods" scopes (and can oftgen see intervening twigs better as well).
On my first hunt in Africa I had my .375's scope on 6x while hunting in some fairly thick thornbrush. At one point the PH looked at me and asked what magnification my scope was set on. I said 6x and he told me turn it down. Instead of arguing I acted like I turned it down, but didn't.
Tell the guide they're 180's. He'll never know the difference.
