c. to change arms: (Military) to shift a rifle from one shoulder to the other.
ΚΠ
1835 Mil. & Naval Mag. U.S. Dec. 80 The overplus of balls is fired by the second rank, which changes arms at each discharge.
2009 Hamilton Mountain (Ontario) News (Nexis) 6 Nov. 1 Slope arms, change arms, present arms and order arms, came the barked commands of the drill sergeant.