Thanks for the advice T.O'Heir. I understand what you mean when you say collecting guns, not calibers. Got that. Example, I have 4 different rifles that shoot 30-06, 4 different handguns and a rifle that shoots 9mm, 4 different styles of 12 GA shotguns. But yes, the majority of calibers I only have one handgun or rifle at this point, and it will probably stay that way. $$
Gun shows... yes, have gotten some great deals at shows on both guns and sometimes ammo, especially rare stuff like 7.7x58 JAP that I picked up cheap at a show one time. Four of my Garand's were great deals I ran into at shows. Living where I do, there is a gun show within an hour drive almost every month SOMEWHERE. Some small, some HUGE with several thousands of tables. As for me needing more money if I want a gun in every caliber?... I prefaced the original post asking for a list of "common or major" calibers. As I said in the post, that's rather nebulous but had to start somewhere. As some have pointed out, I already have some "minor and uncommon" calibers. I probably wouldn't call the 5.7x28 for my FN handgun all that common, but it was an interesting handgun, unique, and I wanted it for the collection. Today I was looking at a Marlin 444P Outfitter, a short lever action gun that takes the .444 Marlin round. Don't think that is a very common round, and such a huge killer cartridge in a rifle that small has gotta hurt shooting it! Don't know much about them. Point being, you are right, I certainly don't have a big enough bank account for a gun in every caliber. Museums do that, not retired guys like me! I took 44AMP's advice and ordered Barnes "Cartridges of the World". Can't wait to thumb through that and read the history of some of the cartridges I now have.