MOUSEGUN AMMUNITION DEVELOPMENT

'Mouseguns' refer to a general category of small pistols - usually having smaller physical dimensions than compact pistols and chambered for less effective calibers. Because of the smaller physical size of these guns, they are likely to be favored over larger guns for the role of backup gun or for civilian concealed carry. The drawback, of course, is that this type of gun is the most difficult to fire accurately and the cartridges fired and short barrels mean that the terminal effectiveness of these guns are among the poorest of all firearm types. The Federal Bureau of Investigation specified ammunition performance standards in the late 1980s, and this standard is accepted industry-wide today. One of the primary provisions of the standard is that a bullet must penetrate to 12" or further in ballistic gelatin before it can be considered to be adequate to stop a determined attacker. While most mouseguns can reach this penetration depth with FMJ (practice) ammunition, with proper ammunition, the risk of overpenetration can be reduced while bullet effectiveness can be increased. To do this, 'bottleneck' pistol calibers can be used to drive bullet to their proper operating velocities. A well-known bottleneck pistol cartridge is the .357SIG - a .40S&W case reduced in size at the end to firmly hold a 0.355" diameter bullet (9mm bullets). By doing this, gun manufacturers can usually just re-barrel existing .40S&W pistols with a 9mm barrel and wind up with a bullet that is smaller in diameter but that travels faster than the bullets fired out of the original case. The primary failure of mouseguns is that the barrel lengths used are too short to propel bullets to the velocities at which they are designed to operate. This can largely be remedied by the usage of bottlenecked calibers - larger powder charges used to push smaller and lighter bullets, largely compensating for the velocity loss of the short barrels. But, of course, there are some pros and cons to this idea. In actual usage, a bullet may not expand at all (due to intervening objects). In this case, a larger diameter bullet is better than a smaller diameter bullet. As an example, an unexpanded .32ACP bullet has a frontal surface area of 0.076 square inches while an unexpanded .380ACP bullet has a frontal surface area of 0.099 square inches - the .380ACP has an area 1.30 times greater than the .32ACP. In this way, an unexpanded .32NAA (the most popular so far of bottlenecked mousegun cartridges) bullet is less effective than a .380ACP that does not expand. But where the bottlenecked mousegun begins to shine is in cases where the bullet does expand (about 66% of the time). When a .380ACP out of a mousegun expands, it will typically expand to a half-inch diameter or larger and penetrate usually no more than 10", which is 2" shallow of the FBI minimum depth of 12". If the bullet does not expand, it can almost always be counted on to penetrate 14" or greater and create a comparatively tiny hole when compared to an expanded hollowpoint. The story for the .32ACP in a mousegun is the same, but worse. In the case of the .32NAA, however, a bullet will travel to 12.5" and expand to 0.45" in diameter without the usage of high pressure loadings. As such, it meets FBI effectiveness standards and makes a hole 1.61 times larger than the unexpanded .380ACP that meets FBI penetration standards. Here are some ideas of mine for new mousegun-specific cartridges, broken down by cartridge: .32NAA The .32 North American Arms cartridge is a .380ACP case necked down to fire .32ACP bullets. The .32NAA is already on the market, with one source of factory ammunition, one source of reloading dies, and two pistols chambered to fire this cartridge. Ballistic gelatin evaluations of this cartridge posted at www.brassfetcher.com reveal that a 2.75” barrel can consistently fire expanding bullets that expand to 0.45” in diameter and penetrate to 12.5”, thus meeting FBI penetration requirements. .25NAA The .25 North American Arms cartridge is a .32ACP case necked down to fire .25ACP bullets. One pistol, a mousegun, is factory available from North American Arms. Cor-Bon appears to be the only factory ammunition currently available for the cartridge – firing a 35 grain Hornady XTP bullet at a purported 1200 ft/sec from a 2” barrel length. If this cartridge were to be loaded with a 50 grain expanding bullet, the performance could compete with the .32NAA in terminal performance (although somewhat less effectively due to the different quantities of powder used in the two cartridges). This can be said if the 50 grain bullet travels around 900 ft/sec because the sectional density of such a cartridge is comparable to the .32NAA using 85 grain bullets. .22BF The .22BF is so-named because I have a tendency to crack very dry jokes – since I’m not aware of any attempts to neck down the .25ACP to fire .22LR bullets, I will call this cartridge the .22 BrassFetcher, for the time being. It is widely assumed that the .25ACP is an ineffective ‘man-stopper’, oftentimes even less effective than the .22LR. This might be the case – the only non-gelatin ballistic ‘test’ that I have seen personally involved one very mad store owner with a Baby Browning and the person who attempted to rob her store at knifepoint. The robber fled when the owner produced her .25ACP. The owner then proceeded to lodge 4 bullets in the back of the robber – the scene was not a pretty one, but the robber did survive and even walked into the ambulance. The .25ACP, when firing a 35 grain projectile out of a 2.75” barrel can be expected to easily reach velocities of 900 ft/sec. Hollowpoint bullets made of pure lead will expand at around 800 ft/sec. www.brassfetcher.com has results posted of 36 grain .22LR bullets penetrating to an average of 14.5” and expanding to 0.281” diameter. Of course, these bullets were fired from a rifle and impacted about 300 ft/sec faster than a typical .22BF round might travel at. Gelatin, being a ‘solid liquid’ subjects bullets to the same drag forces that water exerts on a boat – the faster you go, the drag from the water increases much more in proportion with your speed. After physically testing this design, further refinement would be made, perhaps in the direction of a 40 grain pure lead hollowpoint bullet, driven to maximum SAAMI pressures for the cartridge.