Well, 30 caliber covers .30-06, .308, 7.62x54, 7.62x39 and .30-30, right? So that's about half my rifles right there. Yes, all different cartridges, but all .30 caliber.
22 caliber covers most of the other half... .22LR, .223, .220 Swift
And 8mm should finish up the collection... 8mm Mauser, 8x56R.