I consider my 308 gas gun to be a designated marksman's rifle. I have 4 P-mags, and 5 steel mags for it. I think that about 180 rounds of ammo for a designated marksman's rifle is about adequate. It probably wouldn't hurt to have a couple of spares, but I sure don't want to be humping much more than 180 rounds of 7.62 ammo, a rifle, water, and gear very far. Maybe if someone would drive me everywhere, and pick me up later I could pack more stuff. But at some point, I gotta be reasonable with myself and say I have enough.