Abstract: A timed round stop for a sprocket fed weapon is disclosed. The round stop pivotable into and out of the ammunition feed path responsive to a control mechanism, for preventing a round being fed to the stripper bolt of the weapon before the stripper bolt is in the correct position to receive it. The control mechanism preferably comprises a ratchet having the same number of teeth as the feed sprocket and mounted for rotation about the same axis and at the same speed as the latter. Rotation of the control ratchet brings each of its teeth sequentially into engagement with a control surface of the round stop. During such engagement, the round stop is held in a position where it blocks the feed path. Further rotation of the ratchet terminates the engagement, and the round stop can then simply be pushed out of the way by the round of ammunition.