First off, let me point out that handgun enthusiasts are quite opinionated, and there are a few points of contentions on the subject. There are some debates that have gone on for decades. For instance, try asking some hunters about the theory of "hydrostatic shock" and you'll get an ear full. So if you are a handgun expert, and you read something in the following that you disagree with, please don't get excited. Just send me an email and we'll try to present your side.
If you are sure you won't hit anything but the space pirate, a standard handgun like a .45 automatic might do. One might think that the recoil would be uncontrollable in free fall, but both Dr. Schilling and Erik Max Francis are of the opinion that such recoil is vastly overrated. In a firefight, you'd be trying to keep behind some cover (or you'd be dead) so you'd be braced in some fashion. Any bracing at all would take care of the recoil. Erik (working with somebody else's figures) calculates that the recoil will spin you at the minuscule rate of a few degrees per second. (bullet momentum 4 kg m/s, fired from 40 cm from the center of the axis, the angular momentum imparted to the marksman is thus 1.6 kg m2/s. Divide that by marksman's moment of inertia, and you get an angular speed of 0.05 rad/s, or less than 3 deg/s.) If you wanted to use your handgun for propulsion, Trip the Space Parasite calculates that a .45 automatic will give 0.12 m/s of deltaV to a 50 kg person.
And if you are a space pirate captain who often has to deal with mutiny, you might want to invest in a futuristic version of a duck's foot pistol. A sidearm that fires on all four barrels over a wide angle with one pull of the trigger is a great equalizer when you are outnumbered.
James Borham has another often overlooked concern:
A conventional bullet has oxidizer inside the shell, it does not require atmospheric oxygen in order to fire. However, conventional handgun lubrication oil will boil away in vacuum, leaving a gummy mess. Unless special lubrication is used, the handgun is likely to jam. This is mentioned in The Venus Belt by L. Neil Smith, and also includes a mention of the effect of a 200 degree thermal shock the weapon undergoes when moved from sunlight into shadow. Thermotolerance of all components in the gun are important, many mechanical devices really don't like the idea of going from room temp to -60°F over a short period of time. The weapon might work shortly after it was brought out of the airlock, then suddenly seize up.
Evan Dorn notes that the lubrication question is not quite as bad as I make it out to be:
In other words, vacuum will do terrible things to a handgun's lubrication, but we don't need no steeenking lubrication anyway. However, there seems to be some controversy on this point, with heated debate between the pro-lubrication and con-lubrication factions.
If one is merely transporting the weapon through a vacuum environment but does not intent to actually use the weapon in vacuum, James Borham has the solution:
Mike Van Pelt says that if protecting the spacecraft from clumsy shots has priority, frangible rounds may be the answer. These have been suggested for use by armed airline pilots, who also worry about the damage done by stray rounds. The Glasser Safety Slug was invented back in the 1970's, the current state of the art is the MagSafe. The good news is that they affect human targets far more effectively than spacecraft hulls. The bad news is that the penetration is reduced to a point where the space pirate's arms can offer their torso significant protection. And if the pirate is wearing body armor your handgun has become almost worthless. To make it worse, certain types of space suits are almost as good as body armor.
There is also the matter of vacuum welding and evaporative bonding and outgassing from plastics, coatings for the barrel, propellants in the bullet. C. James Huff notes that a conventional firearm will overheat far more rapidly in vacuum, making an assault rifle practically worthless. James Borham points out that in vacuum a laser weapon will overheat even more rapidly than a conventional firearm.
Other novels mention special muzzle brakes that vector the exhaust in useful directions. These novels include Eon by Greg Bear and Nightrider by David Mace. They generally try to vent in an "X" pattern centered on the tip of the barrel with the arms of the X perpendicular to the barrel. This tries to stabilize the barrel while not allowing the exhaust to obscure the sight picture.
Also note that a handgun for vacuum use will require an over-sized trigger guard to accept a space suited finger. András Bónitz mentions that many pistols today have large trigger-guards for gloved hands. However, a space suited finger is huge compared to a gloved finger.
Nightcrawler points out that revolvers might not be popular in free fall, since other weapons eject their spent cartridges. Hot brass flying around the compartment could cause all sorts of problems. A cartridge floating inside a control panel and shorting out a critical component could ruin your entire day.
This is total space opera without a scrap of real science, but I couldn't resist.
The good old MBA Gyrojet pistol is worth looking at. This out of production weapon actually fired rocket bullets. It had practically no recoil, but alas, as we saw, recoil isn't a problem. The tail jets were angled to spin the rocket bullet in lieu of rifling. Problems included slow burn times (which meant if your target was too close, the bullet didn't have enough time to get up to speed) and poor accuracy.
As it turns out, the poor accuracy was due to the ammunition, not because rocket bullets are inherently inaccurate. The MBA ammo suffered from shoddy manufacturing and poor quality control.
The pistol had a mass of 0.4 kg. The pistol holds six rounds in the magazine. Each .50 caliber rocket "bullet" had a mass of 9 grams (6.65 grams of rocket + 2.5 grams of propellant). Each rocket has a low velocity at the point where it exited the muzzle, but by the time it had traveled 9 meters it had accelerated to 380 m/s.
But with some development, the weapon might be redeemed. The Deathwind project is attempting to create the next generation of gyrojet weapons. Or if you prefer the brute-force approach, the rocket bullets could be enhanced with explosive warheads or made into radar-guided or heat-seeking missiles.
Coridon Henshaw suggests special fusing for the explosive warheads, so the shaped charge will go off if they contact flesh or body armor, but not if they hit the hull. He says another possibility is a multispectral sensor and sighting laser that will disallow firing if the line of sight ends at something that is part of the spacecraft. Include a manual override in case some diabolical space pirate figures out how to make their body armor look like hull plates.
The Gyrojet did have a remarkably jam-proof design, due to the small number of moving parts. Instead of a movable firing pin struck by a hammer, there is a fixed pin at the back of the chamber. The hammer strikes the front of the rocket, forcing it back onto the fixed firing pin. The rocket shoots out the barrel, simultaneously re-cocking the hammer. The hammer is initially cocked by a lever on the side of the sidearm, in an arc-like groove above the trigger.
What caused the MBA company to go bankrupt was the fact that the military didn't want the Gyrojet, and there was no civilian market for a weapon whose ammunition costs over a dollar a shell, with no possibility of re-loading the shells.
Erik says another possibility would be some sort of flechette weapon. This is kind of a shot-gun that fires a swarm of darts instead of buckshot ("flechette" is French for "little arrow"). They look like nails. In the shell, a group of flechettes are held together by a plastic frame called a sabot, which falls away when the load exits the muzzle. Light flechettes are twenty to a shell, heavy are six to a shell. Like shotgun shells, they are good for causing large amounts of damage to the intruder in one's apartment, but failing to penetrate the wall so as to not annoy the neighbors. Unlike shotgun shells, they are good at penetrating body armor.
Well, the heavy ones are good at penetrating. James Borham has further details:
SF author Michael Z. Williamson begs to differ.
Mr. Williamson cites The Box O' Truth as his source. They do test fires on a lot of weapons, for penetration and damage.
In the "visually impressive" department, we have the Whitney Wolverine. At .22 calibre it has no stopping power, but boy, does it does it look futuristic!
The legendary Gharlane of Eddore once said:
In reference to the top picture at the right he said:
Interestingly enough, the Whitney Wolverine is now back in production from Olympic Arms.
The pistol grip of the Wolverine may look weird and futuristic, but it has an ergometric design, and is reportedly quite comfortable to hold.
Keep in mind though that when a SF movie director on a budget uses "exotic" (i.e, not commonly encountered in the United State) firearms as props instead of making them from scratch, they run the risk of the infamous "I Know That Gun" problem. This is when you get a steady stream of gun enthusiasts pointing at the movie screen while saying "I know that gun..." There is a nice list here, and another one here.
Recently, the Beretta company released a target/plinking pistol with the same futuristic look as the Whitney Wolverine. Called the U22 Neos, it too would not look out of place in a spacecraft.
Zathras9 brought to my attention another visually impressive firearm: the Magnum Research Lone Eagle.
The weapons can also have a mystique about them. Pictured is the legendary Cosmo-Dragoon from the anime of Leiji Matsumoto. His astro-automatic is a variant on this. The weapon was modeled after the Colt 1848 Dragoon Pistol. In his anime, there are only four of these weapons in existence, and they are the only weapons capable of killing a machine person. It is truly a space warrior's gun.
Nightcrawler has found several marvelous firearms that were perhaps ahead of their time, but never quite made it. They would be very appropriate for a classic future setting. Nightcrawler advises anyone doing research into such historical firearms to go to Maxim R. Popenker's the "Modern Firearms & Ammunition" site.
Most of these firearms feature the "bullpup" arrangement, where the magazine and the action (mechanism) are behind the handgrip and trigger, instead of in front as is conventional. This shortens the weapon's total length and improves the balance. As a drawback, most bullpups have a specific "handedness". If a left-handed shooter tries to fire a right-handed bullpup, the bullpup will insert the red-hot spent casing up their nose, grab their ear, and attempt to load it into the firing chamber. RanulfC tells me that 90% of all bullpup designs can be easily reset from one handedness to the other.
For an in-depth look at advantages and disadvantages about the bullpup, read Anthony Williams' article.
András Bónitz has also be doing some studying of futuristic looking weapons.
Thomas L. Nielsen (B.Sc. / Case Officer of the Danish Defence Acquisition and Logistics Organization, Weapons Technology Branch ) disagrees with the feasibility of the mercury rounds.
Back to András Bónitz:
Thomas Nielsen had these comments on hollow point rounds. First off, as he stated above, mercury rounds are not weaker than hollow points. Secondly, the proper term is "soft-nosed" rounds, not "soft-headed" rounds. Further:
Back to András Bónitz:
Nuwan Weerahandi mentioned the XM8 rifle, a modular rifle system under development by the US Army. One of the XM8's unique features was its modularity. This modularity allowed for quick repairs, barrel length changes, and even caliber changes in the field. But for our purposes, it is admirably futuristic looking.
These are a few weird rifles I personally have stumbled over.
The Neos has an optional kit that will convert the pistol into a carbine. People who grew up in the 1960's will quickly spot the similarity to the U.N.C.L.E. Special carbine, arguably the most famous of all TV show weapons. And though it was never shown in an episode, the carbines used in the cartoon Johnny Quest can telescope down into a pistol.