What's the point of standardizing? Buy as many different calibers as you want, and then stockpile ammo for each of those calibers that you intend to shoot (not just collect). What benefit does standardizing give you? If you're going to standardize on the caliber, why not standardize on the specific gun as well? Buy two of your standard handgun (one as a spare) and get rid of the rest. There, ... now you're fully "standardized".