Before choosing caliber and handgun type, decide what Division you want to compete in. Simply stated, the rules set out Division specific requirements such as action type, max. handgun size, minimum trigger pull weight, sighting system, compensator.
Then research IPSC's rules regarding Power Factor -Minor PF or Major PF- and remember that these rules are also Division specific. Generally, the greater PF loads yield more recoil which tends to slow you down unless your Div. allows a compensator. On the other hand, a greater PF usually cycles the gun faster... Whatever Division you choose, you will benefit by loading your own so that you get the most out of your HG.
Generally:
- In Production Div., 9mm Minor seems to be the most advantageous.
- In Standard Div., .40 makes Major and is very popular.
- In Open Div., .38Super makes Major and is very popular.
- In Revolver Div., 38Special is very popular.
- Using a Major load in Production is a disadvange.
- Using a Minor load in Standard is a disadvantage.