Pistol competition may be fired outdoors or indoors. The course of fire is basically the same, but the distances are different. Equipment Section 3 of the NRA Pistol Rule Book defines authorized equipment and ammunition. This section is not meant to restrict equipment but to define limitations. Up until about 30 years ago the revolver was the one to use.
Some competitors still use a revolver, but the autoloader is now used almost exclusively.
Autoloaders have been developed that are capable of top-notch accuracy. This is fired with .22 caliber rimfire, center fire, and .45 caliber pistols. However, it is not necessary that you have 3 different guns. In most tournaments you may enter and fire only one or more stages of the aggregate. Many competitors entering complete aggregate only own a .22 and .