Keith settled on the .44 Special cartridge as the basis for his experimentation, rather than the larger .45 Colt. At the time, the selection of .44 caliber projectiles for hand-loaders was more varied, and the .44 Special's brass was thicker and stronger than the dated .45 Colt case. Also, the .44 Special case was smaller in diameter than the .45 Colt case. In revolvers of the same cylinder size, this meant that the .44 caliber revolvers had thicker, and thus stronger, cylinder walls than the .45. This allowed higher pressures to be used with less risk of a burst cylinder.