A mousegun is most often considered a category of small revolver, or semi-automatic handgun intended for concealed carry (CCW)self defense. Typically such small pistols are of .380 ACP (9mm Short) caliber or less, with .32 ACP, .25 ACP, .22 Long Rifle and .22 Short calibers also being common. The term is used to describe a class of small handguns. The term is also sometimes used to refer to rifles firing bullets smaller than .30 caliber, such as the .223/5.56mm.
The popularity of so-called mouseguns has exploded, coinciding with the increasing popularity of concealed carry weapon (CCW) permits, relaxed CCW attitudes by law enforcement and society, and new mousegun weapon design improvements exemplified by the new tiny, under-$250 Kel-Tec P-3AT .380 ACP caliber handgun described in 2003 by GunBlast.com as "the best defensive pocket auto made anywhere, at any price." The .380 ACP cartridge is arguably considered by most gun writers to be the smallest caliber pistol that is safe to use for self-defense. In this case, gun size and weight follows caliber size.
Among mousegun users, the term mousegun is not usually considered to be pejorative, but is instead affectionately used. Manufacturers of these guns however generally label them as "ultra-compact", avoiding the derogatory connotation given by users of larger-caliber, larger-size guns, and also differentiating them from "sub-compact" models such as the Glock 26 and 36, which have a similar role of deep concealment, but fire larger "defense caliber" cartridges between 9x19mm Parabellum and .45 ACP and are therefore slightly larger themselves.
There has been a long-standing and lively debate between the gun owners who prefer larger guns and those who prefer smaller guns for self-defense. (There is a similarly heated debate regarding hunting calibers.) Those who favor larger, heavier handguns (not necessarily of larger caliber) do often use the term mousegun for any small caliber firearm in a disparaging way. They often equate the home and personal self defense roles with military and police roles where both 1) armed conflict and 2) armed conflict with a heavily armed opponent should be prudently expected and prepared for, where indeed power should be considered more important. For this reason many "big gun" fans often carry additional ammunition. Indeed, if one expects imminent armed conflict, handguns will normally be abandoned in favor of extremely more powerful long guns. Within that concept lies the entire debate. In contrast, "mousegunners" typically do not think in terms of a Hollywood gunfight (where the armed opponent needs to be quickly incapacitated) but in terms of having an advantage over going unarmed. In those scenarios, usually zero, to just a few shots would be fired to achieve that advantage. So mousegunners typically carry no spare ammo. Note that few of the advantages of a mousegun applies outside of the arena of CCW, so a "mousegunner' is likely to prefer bigger guns, even shotguns for say; home defense or sport shooting.
Among those who prefer larger, heavier guns, it is noteworthy to realize that .22 caliber pistols (and even rifles) that are intended for target shooting, plinking, or small game hunting are not considered mouseguns. In this usage, there is widespread agreement, even among those who favor the use of mouseguns for use in deeply concealed carry; full-size handguns and rifles, despite firing small caliber bullets, are not mouseguns.
In order to create such small pistols, compromises in the list of features wanted on a gun needs to be made, so many mouseguns lack features such as slide stops and external safeties, and few function quite as reliably as the famously reliable, full-size designs such as the Glock 17 service weapons. The small size and mass of the pistol, and low energy of the smaller cartridges, also could make functioning of semi-automatic versions less reliable. Yet even with the short sight radius and low-profile, snag-resistant iron sights, which are required for meeting the needs for a concealed handgun, some of these mouseguns can shoot 2-inch (5 cm) groups at 21 feet, (6.4 meters,) a typical urban combat distance. It's even possible to shoot a one hole group at 8 - 10 yards (7 - 9 m) with a mousegun.
Many people carry mouseguns for defense on the premise that a weaker pistol that one can easily carry and conceal is far better than a powerful gun you leave at home because it cannot be easily or comfortably carried all day long. Favorite sayings among mousegunners include: "The .380 in my pocket has more stopping power than the .44 magnum in the trunk of your car." And; "Remember, the first rule of a gunfight is… Have a gun." Additionally, many Concealed Carry (CCW) permits require that the gun be fully concealed and that by all appearances the person is, not carrying, also makes the mousegun choice more attractive. And the engineering required to build such a small handgun is admired by many, while many people just enjoy collecting and shooting mouseguns.
Examples of well respected mouseguns include the Seecamp, the North American Arms Guardian and Mini Revolvers (such as the Black Widow), the Kel-Tec P32 (.32 caliber) and P3-AT (.380 caliber), the Ruger LCP (.380 caliber), the Beretta Bobcat (.22 or .25 caliber), Jetfire (.25 caliber), and Tomcat (.32 caliber). Slightly larger 9 mm mouseguns, still under 16 ounces (450 g) in weight, and very small in size, include the Kel-Tec P11 and PF-9, the Smith and Wesson PC 945 Micro, Kahr Arms PM9, and the Rohrbaugh R9. The Rohrbaugh R9 is currently the smallest 9 mm pistol on the market, replacing the Kel-Tec P11 which formerly held that distinction. All of these mouseguns conceal especially well. Mousegun-pistols in .45 caliber exist too; examples include the Kahr PM45 and Para-Ordnance p6.45 and p10.45. When firing these weapons, one should however expect a surprising kick from such small calibers, due to their high power/weight ratio.
Law enforcement mousegun users typically choose guns in either 380 ACP or 9 mm, depending on the rules set by each department for backup guns. Often, the requirement is that the backup gun has to be in the same caliber as the main service pistol, for ammunition compatibility.
Examples of revolver mouseguns include the North American Arms Mini Revolver, which is a spur trigger design with birdshead grips. The North American Arms Mini Revolver is styled very much like popular pocket revolvers of the 19th Century, but is made entirely of stainless steel.
Smith & Wesson's "J-Frame" series of revolvers are a common choice for mouseguns. They are generally more reliable than their automatic counterparts, and offer an exceptional power-to-weight ratio, especially the lightweight AirLite and Airweight lines. On the other hand, they offer only five shots (auto mouseguns often hold more rounds), and have considerably greater recoil, especially in .357 magnum.
Particularly small and high-quality examples, such as the Seecamp LWS 32 .32 ACP pistol, formerly commanded prices significantly higher than its US$600 retail. During the mid-1990s, demand so far exceeded supply that contracts for guns were sold up to two years before the guns themselves were produced, and the guns themselves were then often resold for as much as $1100 USD upon delivery.
Since roughly 1995, however, there has been considerable erosion in these high mousegun prices, no doubt a result of Kel-Tec starting to produce a 9 mm mousegun, the Kel-Tec P11, then the .32 ACP P-32 (~$230) and the .380 ACP P3AT (~$260) in 1993, all of which were priced at roughly half the price of the Seecamp LWS, while packaged in much the same size. As of Sept, 2013, the Kel-Tec P-3AT with its unloaded weight of 8.3 oz. (235g), is still advertised as "the lightest .380 Auto pistol ever made."
- Jeff Quinn's gun review at GunBlast.com, Sep 2, 2003, "Kel-Tec P3AT - The World's Lightest .380 Auto Pistol" "Kel-Tec has done that which almost everyone else said could not be done:..." "With most states passing right-to-carry laws,..." retrieved Sept 11, 2013
- Video Review Uploaded on Sep 15, 2008 by Nutnfancy: "A Nutnfancy Tactical Clinic shoot." Shooting the Kel-Tec P-3AT .380: Reliable Backup Field testing a tiny new Kel-Tec P-3AT, watch Nutnfancy shooting 2-inch and 3-inch groups at 7 yards. Retrieved Sept 11, 2013
- Video Review Uploaded on Feb 1, 2009 by Nutnfancy: Shooting Ruger LCP .380: "Amazing Accuracy" Field testing a tiny new Ruger LCP .380, watch Nutnfancy shooting 2-inch (one hole)groups at 8 - 10 yards (7 - 9 m). Retrieved Sept 11, 2013
- gunblast.com "Have a gun. If you can’t reach yours, it is useless to you."
- KeltecWeapons.com The P-3AT .380 "is mainly intended for plainclothes police officers as a secondary weapon, or for concealed carry by licensed citizens." Retrieved Sept 11, 2013