A weapon for firing cased telescoped (CT) ammunition includes a barrel, a chamber member and a carrier assembly. The chamber member defines a chamber for a CT round for firing, and translates between a firing position aligned with the barrel and an ejection/loading position. The chamber member is spring-biased toward the firing position. The carrier assembly carries the firing pin and (1) performs a recoil in which a carrier and rammer move rearward from a battery position to bring the next CT round into a ramming position and to move the chamber member from the firing position to the ejection/loading position, and (2) performs a counter-recoil to return to the battery position and cause the rammer to push the next CT round into the chamber. The chamber member is released for biased return to the firing position for a next firing cycle.