Patent attributes
A gas-operated firearm has a barrel defining a bore with a gas block defining a chamber communicating with the bore via a gas passage. A gas regulation element has a first position and a second position, and serves to provide different gas flow characteristics in the different positions. The latch element gives the user audible or tactile feedback upon installation of an accessory device when the gas regulation element is a correct position suited to use of the accessory, and not when in the other position unsuited to accessory usage. The accessory may be a sound suppressor, and the latch may serve to secure the gas regulation element against position change. The latch may engage a circular array of elements on the rear face of the suppressor, and may have an angled cam face to provide ratcheting engagement for installation, and to resist removal or loosening without deliberate actuation of the latch.