If your gun doesn't fire, there are only a few possible causes.
Your mag. wasn't seated and you never did chamber a round. CLICK. Or you chambered a round, topped of the mag. and failed to fully seat it. Then it's BANG, CLICK.
Bad primer.
Slide didn't go into battery-- possible feed problem or smoke stack failure to eject the case that prevented the slide from closing.
At the range you can easily diagnose the problem and fix it.
In a gunfight, you don't have time to diagnose.
The tap, rack and bang clears the above of malfunctions and gets your gun working again.
Tap seats the magazine.
Rack gets rid of the hung up round if there is one, and chambers a new round. It will also clear the smokestack, though if you observe the round caught in the slide, it's better to wipe it clear with your hand or turn the gun so it will fall out when you retract the slide.
NOTE: A double feed drill is different, and requires locking the slide back, ripping out the mag., working the action to clear the round, and inserting new mag. and chambering a round. Some pistols allow for ripping out the mag. without locking the slide back (Glocks). But on others, like SIG's, the top round in the mag. is probably too far forward and is hung up by the feed ramp. You have to lock it back to pull out the mag.
These drills have to be practiced. The dbl. feed drill takes a little longer to get down. Practice with dummy rounds.
NOTE: for liability reasons, the new version is Tap, Rack and Decide (if you still need to shoot). There was a case were an officer's gun jammed, he did the TRB. Problem is, that by the time he did the bang part, Bubba had quit fighting and wasn't a threat.
The officer's dept. hung him out to dry and he was charged. His attorney pointed out that he'd followed his training in clearing malfunctions to the letter--including the BANG. He was, I believe acquitted at trial.
Now, all training course teach that you tap, rack, and DECIDE if shooting is still appropriate.
Just as we practice draw and shoot, AND draw and not shoot, maybe we should give some thought to Tap, Rack, and hold our fire, along with TRB, lest we train our selves to be robotic with these actions.
Just my thoughts on the matter.
