While we hope we never have to defend ourselves with lethal force, we know that self-defense shootings average 3-5 shots.
Our local range only allows double taps, no rapid-fire. I understand that for the safety factor, but it creates a bad training habit.
Justin does an awesome job of coming back to the target rapidly in the Now Drill video:
I can do 6-6-6 drill at my indoor range. (adjusted a little - go from low ready position instead of holster).
3 shots, reload, 3 shots (or 4 shots, reload, 2 shots).
If you can double tap then you can conduct multiple target drills. Post-It-Note’s (PIN’s) are great for this. Put 3 PIN’s at random locations on a standard B-24 target. Double tap each one and move to the next.
FWIW And I don’t care if they are acclaimed USCCA gunfighters I can find NO, ZIP, ZERO, NADA (to quote @Dawn) reason to dump 15 rounds on a single target and go back for one more in a defensive or even a combat environment. Dare I say in a court of law you are in a world of hurt and will be the poster child for large mag bans.
Reloading in the middle of your magazine means you have found cover and want a full stack. DO NOT practice dumping a mag for the sake of a DRILL. Design your drills to incur an empty magazine condition with a full magazine, add targets.
IDPA & 3 Gun are one thing where you introduce “SCENARIO’S” practicing for self defense is another. Don’t let the “Game” interfere with reality.
Cheers,
Craig6
My local range will allow you to do certain things they don’t allow others to do if you pass the RSO evaluation and test.
Honestly……….
I show up to my scheduled AM RSO shifts an hour early and put in any “tactical/street” work I need to prior to opening the range or on range closed days (RSOs are allowed access to the range during off hours between 8a and 1hr prior to sunset)
One of the benefits of volunteering (so my volunteerism isn’t completely altruistic 
)
we have no restrictions on number of shots fired ,so I train accordingly
My local range has private lanes that allow for rapid fire and drawing. Double tapping is cheaper either way though 
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I like your logic. I have never understood people who do mag dumps. Just a different personality I suppose, Maybe having someone load a couple dummy rounds here and there would force the issue. My experience would likely be I would have the same number of “good” shots doing 4 round “dumps” as I would doing 15 round dumps.
Whats the old joke? Why did you shoot him 25 times? Because I didnt have 26 shots.