The only ones that I have multiples of are the 30-06 and the 45-70. The 30-06s I have are a Pre64 M70, Sako AIII, and a Garand, and the 45-70s are an original Rolling Block, a Shiloh Sharps, and a Browning 1885. In both cases, I have to pay attention to my ammo to ensure that the ammo from A or B doesn't end up in C. In the case of the Garand, the potential to damage the op rod means that you want to keep your ammo well separate from the hotter hunting ammo for the two sporters. The 45-70s are a similar situation, btu with more catastrophic potential. Loads for the Browning are hot...420gr cast bullets at 1950fps. Needless to say, we don't want to have one of those find its way into the Rolling Block. I'm fairly confident that would be a very bad day. I've taken the precaution of labeling the MTM box with a warning and I use nickel plated cases for that ammo, so I should be fairly certain to get the ammo choice right. The Sharps would probably digest those loads safely, but there's no point of putting that kind of wear and tear on that rifle. So the BPCR ammo gets stored in one place, and the smokeless in another.
Aside from these scenarios, I don't see much point in duplicating cartridges. Maybe if we lived somewhere that you could use an AR and you wanted a separate 223 platform for varmints or predators. Same if you had a 308 or similar for hunting and another for target shooting. But to own two hunting 30-06s is just a little pointless. And, yes, I acknowledge the irony of me saying that.
