 Bushmaster requested the ammunition manufacturer Hornady to produce the .45 Professional cartridge for this project, but Hornady wanted to shorten the cartridge case and overall length to accommodate their 0.452" 250-grain pointed SST Flex-Tip bullet.Bushmaster and LeGendre approved the change from a 1.772" (45mm) case and 2.362" (60mm) OAL to the now standard 1.700" (43.18mm) case and 2.260" (57.40mm) OAL.This permitted operation in the more abundant and popular AR-15 platform versus the AR-10 platform.