Tap rack bang

Tap, rack, bang (TRB) or Tap, rack and go is jargon for the response to a failure to fire in a firearm with a removable magazine.^[1] This is designed as an unhesitating "Immediate Action" and involves no investigation of the cause; but is effective for common failures, such as defective ammunition or improperly seated magazines.

1. Tap - to tap the magazine. This is to ensure that the magazine is properly engaged in the firearm so that it feeds properly. As typically taught in tactical firearms courses, the "tap" is considerably more than a tap and in the case of a semiautomatic pistol is usually accomplished by slamming the gun hard into the palm of the other hand, magazine end down.
2. Rack - operating the action of the firearm. This will serve to eject a misfired round, which could be a possible cause of the stoppage, and chamber the next round.
3. Bang/Go - aiming and firing the firearm again. If the firearm again doesn't fire or fails to extract the spent round, it may indicate a more serious problem with the firearm requiring maintenance. For instance, if the firing pin is too lightly striking the primer on a cartridge, it may indicate a worn out spring or firing pin.

Some failures, such as a "stovepipe", require more complicated maintenance or attention from a gunsmith; and with others, such as a squib load the "tap rack procedure" should never be used.^[2]

References

1. Tong, David, "Trigger Options of the Semi-Automatic Service Pistol"
2. "IMMEDIATE AND REMEDIAL ACTION - M9 SERVICE PISTOL", Marine Corp Development Command, p. 7, archived from the original on 2014-03-17, retrieved 2016-03-07