On sticking with limited calibers, that's a great idea! I used to be a .45 snob, and still have several 1911s, but The Browning Hi Power lured me away like an exotic European stripper from a stout Midwestern farm girl. I recently bought a 9mm carbine and it's surprising how much range you can get from standard 9mm ammo with that longer bore. You gain about 200 fps over pistol velocities, so essentially standard 9mm becomes hot +P ammo, and +P ammo becomes crazy hot +P+ ammo. I don't know what +P+ ammo would get you, because I worry about wearing out gun actions with too hot ammo. With standard ammo, that carbine will easily make head, er, coyote, sized groups at 100 yards with essentially no drop if zeroed at 25 yards. +P ammo extends the range to 150 yards. I'm currently awaiting some specialty 9mm ammo designed for carbines using very slow pistol powders (to take advantage of that long barrel) that claims to reach out to 200 yards, and does that with fairly low pressure just taking advantage of the longer burn time. I have a number of guns in a variety of calibers, but if I didn't and was thinking of just two guns, a handgun and a long gun, I think two 9mms might be a good choice. 9mm ammo is cheap and plentiful, and since so many of these 9m carbines are hitting the market right now the competition makes them quite inexpensive compared to ARs and what-not. The other cool thing is that many of these carbines use the same magazines as common handguns, so just that much more interchangeability. .