A firearm impingement apparatus that includes a gas flow control member that is operable to provide incremental adjustment of gas flow within the gas block of the firearm impingement apparatus wherein the gas flow control member is configured to provide calibrated rotational movement thereof. The gas flow control member further includes a first portion, second portion and third portion contiguously formed. The first portion includes a plurality of longitudinal indentations circumferentially disposed thereon. The second portion has a diameter that is less than that of said first portion and said second portion. A mounting member is present adjacent an opening of a channel and includes a control pin biasly mounted therein that is operable to engage the gas flow control member. The control pin engages the longitudinal indentations to provide calibrated rotational movement of the gas flow control member.