Kinetic energy bullets are made from steel, tool steel and depleted uranium and need a sabot to protect a firearms rifling. Above are four .22 caliber steel bullets in sabots and loaded into 30 caliber cartridges and one .30 caliber steel bullet in a sabot and loaded into a 357 Magnum. The ideal weight for a .224 inch steel bullet core is 55 gr. and the ideal weight for a .308 to a .312 inch steel bullet core is 110-gr. and up. The length of the bullet is dependent on the sabot 2/3 of the bullet should be in the sabot, if the bullet core is under that depth it can yaw (spin erratically). The reloading data for the 22/30 caliber is available on the Internet or with the sabots when you purchase them. The reloading data for the 30/36 caliber (9 mm, 38 special and 357 magnum) or larger is available in reloading data manuals by weight of bullet. Sabots come in a range of American standard calibers from 22/30 to 50/54 and are available in stores all over North America.