Brass Fetcher
Member
Here is a little article that I wrote regarding some of the issues regarding the production of effective ammunition for mouseguns.
Please tell me what you think. I will probably post this to the website if it looks good to you all.
Thanks. JE223
Please tell me what you think. I will probably post this to the website if it looks good to you all.
Thanks. JE223
The Importance of Mouseguns and Ballistic Testing
With the recent reforms of concealed carry laws in more than thirty of the United States, more people than ever are choosing to exercise their constitutional right to keep and bear arms. Due to a number of factors, a likely majority of the arms that are used for concealed carry gravitate towards the smaller frame pistol, which is given the often affectionate title of ‘mousegun.’ Mouseguns are appealing because they are the smallest and lightest of all guns and are thus easiest to conceal on ones person and to carry around for hours at a time. However, as they say, there is no free lunch. Such handguns often have shorter-than-normal barrel lengths which produce lower-than-normal bullet velocity, fire a cartridge that is less powerful than the more common cartridges found in ‘service’ and ‘compact’ handguns and typically have very rudimentary sights – so firing an accurate shot is also more of a challenge with this type of gun. Most pressing of all and bordering on a moral issue for those involved in ammunition development is the necessity of maximizing the effectiveness of these diminutive calibers for the sake of their most frequent user – persons who want a gun for protection but are not typically ‘gun people’, females wanting a gun for protection but favoring the mousegun for its non-imposing appearance and people of a physical stature that makes harder-recoiling firearms unshootable. These people are less likely to be able to defend themselves in close-quarters with an adversary that has been shot and keeps attacking, than is a police officer or other person in a state of better physical conditioning.
As such, the need to insure the reliability of defensive ammunition for such guns is more important even than for the larger-sized handguns. The first order of business then, is to ensure that the chosen load will be able to penetrate twelve inches or deeper in a block of ballistic gelatin. Ballistic gelatin is the standard test medium for such concerns and the twelve inch depth is a performance benchmark to ensure that acceptable bullets will penetrate deeply enough to reach the vital organs of a truly psychopathic attacker – the one who will not cease an attack at the sight of your gun. Second in importance is to maximize the size of the hole left by the bullet. This is done by utilizing expanding bullets such as hollowpoints and/or designing the face of the bullet to be as blunt as possible. While the first and most important goal of adequate penetration is usually achievable by the use of FMJ ‘practice’ ammunition, the second goal of expansion is much more difficult to achieve and is largely what drives this article.
The primary factor in handgun ammunition expansion is the velocity at which the bullet impacted the target. Reliable expansion for any expanding bullet generally begins at 700 ft/sec. While most every bullet in any caliber travels faster than that, the story begins to change as the barrels begin to get shorter. Ammunition manufacturers typically utilize ‘test barrels’ with barrel lengths of four inches and longer to fire their bullets during the test and evaluation phase. An example might illustrate this difference: out of a 4 inch test barrel, cartridge ‘A’ travels at 1000 ft/sec. When cartridge ‘A’ is fired out of a real barrel (2.75” mousegun), it travels at an average velocity of 829 ft/sec. ‘A’ will expand and penetrate to 13”+ in ballistic gelatin out of the test barrel, but will not expand at all and penetrates to 16”+ in the 2.75” barrel of the actual handgun. While the penetration is good, a potentially more effective wound is not created by the narrow diameter of the unexpanded bullet.
Considerations and approaches to a solution
Velocity from short barreled pistols remains the primary challenge to bullet performance. This can be compensated for by using a faster burning powder and using more of it. For whatever reason, it seems that factory ammunition made in the United States for the common mousegun calibers of .25ACP, .32ACP, and to a lesser extent, .380ACP is loaded to lower operating pressures than comparable ammunition made in Europe. It has been suggested that this is to limit any liability that might arise from the usage of high pressure ammunition in older guns (some of these calibers date back to the turn-of-the-century) or in guns made of dubious materials and with shoddy design practices.
These two birds can likely be felled with one stone – the bottlenecked pistol cartridge. A bottlenecked cartridge is made by taking a ‘straight walled’ cartridge case, which closely resembles a pipe in shape, and collapsing the end of the cartridge down to fit snuggly around a slightly smaller bullet. This allows a shorter barrel to propel a (usually) lighter bullet to its proper operating velocity, allowing the mousegun to fire a bullet that will expand and make a larger hole than the unexpanded full-caliber bullet would have made, while still penetrating deep enough to be effective against a determined attacker. At the same time, the new bottlenecked cartridges could be dimensioned such that they will not fit in an older gun designed for the parent cartridge – allowing full pressure loads from the factory to be sold with the knowledge that they can only be used in barrels of modern manufacture.
Some examples of this idea that are currently on the market, as well as some proposed concepts are listed below.
.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.
