the term "windage drum": a misnomer
It exists as part of the rear sight system for M16/AR-15 A1 type rifles. It has five detent holes around it.
It's not a KNOB (as on the A2 rifles) as it can't be turned with the fingers but requires a tool as a nail to adjust windage.
If I were to have named this part, I would have called it a WINDAGE WHEEL instead as it is round, revolves and is relatively flat.
DRUM is a better term for a rotating mechanism that is more cylinder-shape: round and thick.
WINDAGE DIAL is a term that might have also worked because it looks much like a telephone dial with the holes around it.
The military probably just likes the word DRUM as it alludes to marching bands and gunfire.
Last edited by Dave_Preston; 04-10-2019 at 06:15 PM.