Patent ID: 7779571

Claim:
An attachment for a firearm having a barrel with a barrel longitudinal axis, said attachment comprising: a mounting assembly having a first mount with a first mount first side and a first mount second side, said first mount having a pin biased to project from said first mount second side in a direction generally parallel to the barrel longitudinal axis; an indexing assembly having a first indexing plate with a first indexing plate first side and a first indexing plate second side, and a plurality of stops projecting from said first indexing plate first side, said indexing assembly further having a rotator, wherein said indexing assembly is aligned with respect to mounting assembly by engagement of said pin and one of said plurality of stops; a first tube; and a second tube, said second tube having a boss within said second tube, wherein when said second tube is emptied, said boss causes said pin to temporarily retract from said first mount second side to thereby enable said rotator to rotate said indexing assembly until said pin engages the next of said plurality of stops.