Manufactured on the M&P15 modern sporting rifle platform, this upper is chambered in .300 Whisper and will also safely fire 300 AAC Blackout. With low recoil and muzzle blast, it was designed to operate with or without a sound suppressor. The barrel has a 1:7.5" twist rate, 5/8-24 threads, and a A2-Style flash suppressor. It is compatible with a wide variety of bullet weights from 110 to 220+ grains. Feed ramps and gas system optimized to run efficiently with a full range of factory loaded sub-sonic and super-sonic ammunition, both suppressed and unsuppressed.