revolver bullets used to be outside lubed, like a .22 is. They had a reduced diameter "heel" on the bullet, like a .22 does. When they got enough comlaints about debris sticking in the lube, preventing chambering, they went with the bullet down inside of the case. that meant either smaller bores, or larger OD barrels, cylinders and frames. It was MUCH cheaper to just use smaller OD bullets.