[Biggfoot44]

The most commonly accepted account is that in the very begining of selfcontained cartridges, they most commonly used heel type bullets, now seen primarily in .22 rimfires. In this type the diameter of the bullet is the same as the outside diameter of the casing. Then after inside seated bullets were introduced (generally considered to be the S&W .44 Russian circa 1869) other mfgs saw the superiority of the situation. For the most part, the case sizes and designations were retained, and bore size was reduced slightly to corespond. There were a few transitional oddities, most notably the .41 Colt family of ctgs, but that's a seperate line of trivia.