Abstract: A mounting assembly for a firearm muzzle attachment includes a locking mechanism. A muzzle attachment can be secured to a distal end portion of the mounting assembly. The mounting assembly is designed to removably attach the muzzle attachment to a muzzle adapter installed on the end of a firearm barrel. A locking mechanism on the mounting assembly is operable by rotating a collar between a locked position and an unlocked position. In the locked position, the one or more pawls engage in a ratcheted action with a plurality of ridges on an outside surface of the muzzle adapter to inhibit loosening rotation of the mounting assembly relative to the muzzle adapter. In the unlocked position, the pawls disengage from the muzzle adapter to permit a loosening rotation of the mounting assembly. A method of use is also disclosed.