Types

• According to Glock, Glock pistols are available chambered in seven different calibers, including 9 mm, .40-caliber, 10 mm auto, .45 G.A.P., .45 ACP, .380 auto and .357. Each of these calibers are available in two to four size classes of pistol, including standard, compact, subcompact and subcompact Slimline.
  
  

Significance

• When comparing Glock chambers, the laws of physics dictate that the larger the caliber of a bullet, the more damage it does to its target if all of its energy is spent in penetrating the target. This translates into one of the most widely debated aspects of self-defense handguns: stopping power, or what the FBI more accurately calls "Handgun Wounding Factors and Effectiveness."
  
  

Effects

• While chamber (caliber) size is an important factor to compare when choosing a Glock, another aspect to consider is the form factor of the pistol as a whole. Compact and subcompact Glocks such as the 9 mm Glock 19 and Glock 26, while much more easily concealable than the standard-size 9 mm Glock 17, achieve this smaller size by sacrificing magazine capacity. This may, for example, affect the desirability of a Glock 19 or a 26 as an everyday carry weapon for law enforcement officers.