Today all "22 centrefires" use bullets of the same diameter, 0.224". The different rounds, ie .22Hornet .222, .223, 22-250, 220 Swift . . .use different cartridges with different chamberings. The 22-250 has, I think, the biggest capacity of any commercial cartridge, although the Swift may still be bigger. .243 is essentially the next step up, at 6mm bullet diameter. 6.5 is the next.
Not very helpful I'm afraid bro. This really is a complex subject! If you want advice on specific calibres get back to us.