In certain forms of competition you will see Power Factor be referenced. This is used to ensure that all competitors are using properly loaded ammunition and to ensure a level playing field. The most commonly used power factors are Major and Minor. While the required Power Factor may change from division to division the way it is calculated is always the same.
(Bullet Weight in Grains x Velocity in FPS) ÷ 1000 = Power Factor (PF)
Major Power factor in USPSA is defined as anything over 165 PF, while minor is defined as anything over 125 PF but under 165. When it comes to STI pistols all pistols are designed for standard factory ammunition with the exception of the DVC Open, which requires ammunition that meets this Major Power Factor. There are several manufacturers that produce ammunition that specifically meets major power factor. Below are links to additional information.