I only have a .470 and would suspect this caliber is by far the most common today. I suppose we can thank Federal for that though the many other fine calibers, particularly the 450 No2, would enjoy a boom in popularity if commerically produced ammo was introduced to the market. Even though most double rifle enthusiasts reload, the market for many of the newer guns, as well as first time buyers, seems to be influenced by the ready availability of Federal .470 ammo.