Mouse Gun. The smallest guns in the weakest calibers. These handguns are amazingly small, which makes them easy to conceal, however difficult to hold properly and difficult to shoot well. Since they are so small, they come in equally small and weak calibers; typically 22LR, 25ACP and 32ACP. While the term Mouse Gun is clearly derogatory, Mouse Guns do have a place in the world. They are not toys and require the same respect and care as their larger bretheren. They can incapacitate or kill an attacker. They are the most concealable firearms extant, which makes them good last-resort weapons. You can take these guns when nothing else will fit, when they must stay hidden at all costs. I'm reluctant to consider them the primary carry gun, however, for some they may be the best choice.
Pocket Pistol, aka "BUG". As the name suggests, the Pocket Pistol is small enough to fit in a pocket. While some refer to Pocket Pistols as Mouse Guns, unlike the Mouse Gun, many Pocket Pistols are available the same calibers as their full-size brothers. Generally speaking the Pocket Pistol is the smallest gun that can be chambered in the more serious calibers, such as 380ACP, 9mm, 40S&W and even 45ACP. Of course, there are pocket pistols chambered in 22LR. BUG stands for BackUp Gun; a reference to their popularity with law enforcement as a backup gun.
Micro 9. The Micro 9 is the newest phenom on the handgun scene. Originated by Sig Sauer with their P365, these small handguns combine the small size of the Pocket Pistol with a new generation of magazine giving the Micro 9 significantly more capacity than the traditional pocket pistol. For example, the original Sig P365 holds 10+1 rounds of 9mm compared to the traditional 6+1. Many gun makers have jumped on this bandwagon, however it seems that Sig still leads the way with ever newer variants offering new features and greater capacity all the way up to 17 round magazines. Besides their greater capacity, the Micro 9's share a thin profile making them more comfortable to carry, especially inside the waistband.
Sub-Compact. The Sub-Compact is essentially a full-size service pistol shrunk to its minimum size. A classic example is the Glock 26. The barrel is as short as possible while maintaining the reliability of the standard service pistol. Likewise, the grip is as short as possible, often just enough for a two-finger grip. Magazines with pinkie extensions are popular. Unlike the Pocket Pistol and Micro 9, the Sub-Compact has the same width as the full-size model, and even accepts the same magazines as the full-size service pistol.
Compact. For many years, the most popular size handgun for most armed citizens, though the Micro 9s are challenging them. The original compact is the 1911 Commander model; the the same gun as the 5" Government model, however with a 4.25" barrel. The Glock 19 is the modern classic and generally considered to be the most popular handgun in the world. Naturally, most if not all gun makers offer a Compact version of their full-size pistol.
Full-Size. The Full-Size service pistol is the handgun found in the holster of almost every street cop, and the sidearm of every soldier. The grip is large enough for the largest hand; too large for many women and smaller-statured men. Barrel length ranges from 4.4" to 5", depending on the gun manufacturer. to get the full performance of their duty ammuntion. Magazine capacity of their standard capacity magazine is typically 17 rounds, though some are 18 or 19. The Full-Size service pistol is measuably easier to shoot and shoot well than the smaller models, thanks to their greater weight that helps absorb recoil energy and greater sight radius that makes accurate shooting easier.
Long Slide Competition Guns. Several gun makers offer long slide versions of their Full-Size service pistol, These models are very popular in the action pistol sports because of the addtional recoil absorbing characteristic and accuracy enhanding longer sight radius. Occasionally, you'll see one of these in a police officer's holster.
AR Pistols, Draco & similar. Most folks that aren't familiar with the National Firearms Act (NFA) are likely to think these pistols are actually rifles. An AR pistol is a type of handgun that is based on the AR-15 design, featuring a shorter barrel and no buttstock, allowing it to be held and fired with one hand. It is classified as a handgun and must have a barrel length of less than 16 inches and an overall length not exceeding 26 inches. A Draco is the same thing, except based on the AK-47 instead of the AR-15. Much larger than a holstered handgun, so they are considerably less convenient for concealed carry, however their rifle caliber ammunition makes them much more powerful. Again, there are many variations including some that are pistol versions of pistol caliber carbines (AR-15s chambered in pistol calibers, especially 9mm)
