The standard lower receiver on an AR-15 platform offers compatibility with numerous calibers, including .204 Ruger, .223 Remington, .22 Nosler, .224 Valkyrie, .25-45 Sharps, 6.5 Grendel, 6.8 SPC, .300 Blackout, .300 Ham'r, .30 Remington AR, .350 Legend, and .450 Bushmaster.