IDPA is a good way to train, however it does set the shooter up for a real-world failure and that's coming from an instructor who shoots IDPA. Let me break the competition shortcomings down a bit for everyone, know that they are not isolated to IDPA as these will apply to IPSC, USPSA, as well as other training options.
Walkthroughs of the scenario (won't happen in the real-world)
The shooter can self-train on scoring zones (real-world vital areas are covered by clothing folks)
Based upon "what if" scenarios - if you can dream it they just might use it
Reacting to a shot timer rather than your personal perception and reaction that a threat exists
In some, you can miss fast enough to win (miss in the real-world and you could wind up dead or in a lawsuit)
Governed by rules (bad guys don't play by the rules)
Rarely does the body give you a proper physiological response in a competition (you will get the response real-world)
So, as long as you're aware of these unrealistic advantages prior to then competitions are a great training tool. Airsoft is another option and yet there are even more options.
Matt Canovi has a book based on his REAL Defensive System. DVD's are available, but to keep it cost-effective for you, the digital copy can be had for less than $7 and will give you the following:
Up close and personal
Point shooting
Front sight shooting
Shooting on the move
Ground fighting
Multiple shots for stopping power
Head shots for stopping power
Multiple threat response
Barrier shooting
Scenarios
.....and more!
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