Pressurized environments are becoming increasingly prevalent in todayís society, and are also increasingly at risk from hostile elements. Airliners, biological laboratories, and submersible vehicles are all currently at risk, and in the future facilities like space stations/hotels, private spacecraft, and underwater hotels will all be vulnerable as well. Weapons specifically designed to operate in such environments may be a natural outgrowth of such security concerns.
But first it may be prudent to clear up a popular misconception about pressurized environments perpetuated by many sensationalist movies, such as Total Recall, Outland, and many of the Airport movies: most pressurized environments will NOT explosively decompress within seconds if one or even several small holes are blown in them. They are all designed with possible blow-outs in mind, and are built with multiple redundancies to reduce the damage punctures can produce.
The one exception to this would be deep-diving submersibles; the pressure in the deep abysses of the ocean is measured in tons per square inch, and a single puncture in a bulkhead there can indeed lead to near-instantaneous disaster.
But this is not to say that punctures are completely nothing to worry about in other pressurized environments. Indeed, if left unattended too long, even a single small hole can eventually lead to a significant drop in pressure and breathable air. In a firefight, a bullethole puncture may end up in an unusual place, such as under a bolted-down seat or behind several tons of cargo or such, that would be hard to get to and repair. Also in vehicles such as an airliner or a spacecraft, the holes blowing out pressurized gas can add unexpected thrust vectors to the craft, making it that much harder to control.
The handguns discussed in this article would probably only be part of an arsenal of weapons useful in taking down targets in a pressurized environment. Non-lethal weapons such a dart guns, pepper sprays, tasers, and the like would be very useful, as they can neutralize a human target with minimal collateral damage. At advanced tech levels, laser and microwave weapons may also be used.
In an enclosed environment like an airline passenger cabin or a space station, weapons like standard handguns with high-velocity projectiles risk penetrating the hull, compromising pressure integrity and endangering the people inside. A Pressure Environment Handgun (PEH) would give security forces culprit-stopping power without endangering the pressurized environment.
Ideally, one would want a weapon that would stop a human-sized target (or a number of them) but not damage bulkheads and vital systems. The weaponís design must also take into consideration that the environments it will be used in will tend to be cramped and contain a relatively high density of civilians. A number of currently existing small firearms would work fairly well, but are not as optimized for such environments.
Pistols, machine pistols, and compact sub-machine guns will be preferred over rifles and carbines because of the cramped spaces involved. Eliminating the need for the weapon to eject a casing, and damaging nearby equipment or personnel, would also be desirable. Revolvers, or automatic weapons that utilize caseless ammunition, would fit the criteria well.
The types of ammunition used in the weapons would be critical. Frangible rounds are designed to break apart upon contact with anything harder than they are, such as a wall or bone, expending much of the bulletís energy into shattering themselves to destruction. They can, however, penetrate flesh and normal clothing just fine. Maximized stopping power with minimal hard-surface penetration.
The main disadvantage of frangible rounds is that they can be easily stopped by simple ballistic armors. Still, the round transfers full momentum upon contact with the target just like any other bullet, creating blunt trauma damage that may still be affective to stopping an assailant.
Caseless rounds were originally developed for Advanced Combat Rifles (ACRs) and are more fully detailed in that article. Basically, the round is surrounded by a sheath of mixed igniter and solid propellant, held together by an advanced binder agent. A metal casing is unnecessary, reducing the roundsí overall weight and bulk significantly. Use of caseless ammunition would help eliminate the need for the ejection of casings while still providing large magazine capacity for the weapons used. A combination caseless, frangible round would probably prove ideal for pressurized environment pistols.
Short-barreled automatic shotguns provide a viable alternative, using high stopping power with low penetration. Again however, these can be stymied somewhat by personal armor. Frangible and non-lethal rubber slugs can also be used with these weapons.
Security in such environments are also likely to have more standard, high-penetration firearms held in reserve to deal with extreme threats, but in most mundane situations (security checkpoints and such), PEHs would be preferable.
Laser and maser weapons, if ever developed, would probably supplant PEHs, as they can deliver greater damage to organic tissue but barely scar metal and plastic unless deliberately "drilled" into one spot. This would be especially true in microgravity environments, as lasers would have no recoil.
Traveller RPG(various editions); "snub pistols"
On The Web:
An article on the use of firearms on airliners:http://news.bbc.co.uk/2/hi/uk_news/3039583