Slugthrowers

Slugthrowers are projectile weapon firearms, i.e., an ordinary gun that shoots bullets.

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.

Refer to the weapon energy and weapon range tables to compare energy weapons to slugthrowers.

Yes, a bullet will fire in space even though there is no air. All the oxidizer the bullet needs is packed into the cartridge.

For an in-depth look at various firearm types past and future, I will refer you to the always worth reading Future War Stories:

Recoil

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. I guess that means it will give 0.088 m/s deltaV to a standard 68 kg person. Firing the entire seven round magazine will give a 68 kg person about 0.71 m/s

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. Naturally a shot gun would work as well.

"Meanderings" points out that since Luna has a gravity 1/6th that of Terra, a handgun with 1/6th the recoil will have about the same kick as a corresponding Terran handgun. Less effect, actually, since the shooter has 100% of their mass even though they only have 1/6th their weight.

Hearing Protection

James Borham has another often overlooked concern:

As RocketCat is so fond of pointing out, everything old is new again. As with so many things, this very problem popped up back in historical times.

Stay with me, this may seem to be a digression but it will come to a point. This is a great observation made by master spacecraft designer Ray McVay.

World War I brought the horror of Trench Warfare, since the fossilized military command structure of all the nations could not cope with the fact that technology had rendered much of military tactics obsolete. A leader could lose tens of thousands of soldiers in a few minutes if he ordered them into the certain death of "no man's land."

But there was an old tactic that would still work. The old medieval tactic used to deal with castle walls: tunnel warfare. WWI combat engineers could tunnel under no man's land and plant bombs underneath the enemy trenches.

Unfortunately, there was an equally old defensive tactic that would also still work: "counter-mines". The defenders can dig a tunnel parallel to the attacker's tunnel. When the attacking engineers penetrated closer to enemy lines, the defenders could suddenly dig an opening into the attack tunnel and ambushed the attackers from the rear.

Above is pictured the Lee–Enfield rifles used by the British soldiers. As you can see they are very long, which is a real handicap inside a narrow tunnel. The Royal Engineering companies would cut down their rifles so they could pivot the rifle without the accursed thing getting wedged into the walls. Because you never know when German soldiers are going to abruptly appear out of the walls behind you.

Now jump forwards about fifty years to the Vietnam War. There were no trenches, but the Viet Cong had created an incredibly extensive network of underground tunnels and complexes. Not just tunnels: hospitals, training areas, storage facilities, headquarters, and barracks. These had to be destroyed by US, Australian, and New Zealand combat engineers, aka "tunnel rats". And in the process, something that was a bit of a problem in WWI became a major problem.

The Lee–Enfield rifles were only .303 caliber. The US tunnel rats were armed with standard issue M1911 pistol with .45 caliber ammo. You discharge that weapon inside a narrow tunnel and you will be temporarily deaf for hours.

Much like a boarding party infiltrating James Borham's starship, actually. Everything old is new again.

In 1967 the U.S. Army issued requirements for a silent, multi-projectile based weapons for use by tunnel exploration personnel. The U.S. Army Land Warfare Laboratory, Aberdeen Proving Ground, in collaboration with AAI Corporation, developed the Quiet Special Purpose Revolver (QSPR). Requirements included reduced blast, noise, flash, but with increased lethality over the standard pistols and revolvers.

Eleven prototypes were made and field tested. Sadly they didn't work very well and the program was shut down. But science fiction writers can postulate a future version that could be standard issue for starship boarding parties.

The final report was classified, but only to the Confidential level. Probably because the weapon buckshot pellets were made out of this new stuff called "depleted uranium."

Propellent and Lubrication

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.

"Meanderings" says that problem can be reduced if you ensure that all moving surfaces in contact are of dissimilar materials (e.g., metal on ceramic or plastic). In addition there are some special surface films that can be used instead of lubricants. It goes on to say that while some materials degrade under temperature extremes, others do not.

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:

Targeting

Back to András Bónitz:

Other

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.

Nightcrawler points out that revolvers might 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.

Vacuum Firearms

Christopher Phoenix (Mechanizoid) found a marvelous US Army study on vacuum firearms full of all sorts of interesting details. The report is titled "The meanderings of a weapon oriented mind when applied in a vacuum such as one on the moon" (1965), from the U.S. Army Weapon Command's Future Weapons Office. The US Army was working on a proposed Army base on the moon and figured the soldiers would need some kind of weapon that would work in the Lunar environment in case of invasion by a Foreign Power.

For other weapons suitable for use in the lunar environment, see this report.

The report was looking into slugthrowers that Army troops could use on Luna. They found it interesting to note that a bullet fired in vacuum retains all of its velocity, since there is no air resistance when there is no air. Here on Terra, the further a bullet travels, the more it slows down, and the lower the damage it inflicts.

Given the Lunar gravity a bullet fired horizontally from the shoulder of a person six feet tall (about 5 feet), the bullet will travel about 2.73 times its velocity before gravity pulls it down to the ground. For example, a bullet with a muzzle velocity of 3000 ft/sec will impact about 8190 feet away.

If instead of firing horzontally you fired it at a 45° angle to the surface, it would impact about 318 miles away, and have a maximum altitude of 79 miles.

At a range of 328 feet the bullet will only drop by 2.4 inches, so a complicated set of gun aimsights are not required.

It is also important to note that the Lunar escape velocity is only 7900 ft/sec. So orbital velocity is 7900 / √2 = 5600 ft/sec. Which is quite attainable by conventional firearms. Therefore Lunar firearms should have a muzzle velocity limited to less than 5500 ft/sec or so, to avoid filling Luna's orbital space with hazardous shrapnel. A bullet could easily destroy a satellite and seriously damage a spacecraft.

Bullets would not need to be sharpened to an armor piercing point in order to penetrate a flimsy space suit, but you might as well sharpen them in case you are shooting at a Lunar rover or habitat. There is a direct correlation between bullet penetration and lethality, since popping the target means death by asphyxiation. At the very least the target is going to lose interest with anything other than plugging the blasted bullet hole.

Vacuum Firearm Problems

In "Meanderings" they note some common problems that people thought would crop up if a soldier tried to use a slugthrower while in the Lunar environment:

1. The temperature ranges from -250°F to +250°F. This will drastically affect the bullet propellant, making the muzzle velocity wildly vary by 24 to 50%

2. The high vacuum environment will make the blasted metal moving parts in the gun weld themselves together

3. The lubricants will evaporate in the vacuum, leaving the mechanism unlubricated

4. The low gravity will mean the weapon will have to be recoilless or it will kick the soldier head over heels

5. The components of the gun will degrade dues to high vacuum and extreme temperatures

6. A directed energy weapon (i.e., a laser pistol) may be the answer

The Future Weapons Office did some research and discovered that many of these problems were bovine excreta.

1. With a bit of shade during the day and Earthlight at night, the temperature range will be a more reasonable -65°F to +125°F

2. Vacuum welding requires the surfaces to be ultra-clean with no corrosion. There are protective coatings that will fix the problem.

3. Yes, lubrication will boil away in vacuum. But in lieu of conventional lubricant, special surface films can be used. In addition, weapon should be constructed so that moving surfaces in contact are composed of dissimilar materials (e.g., metal on ceramic or plastic).

4. Luna has a gravity 1/6th that of Terra. So as long as the weapon has a recoil which is 1/6th that of a comparable Terran-rated weapon, it does not have to be actually recoilless.

5. Some materials do degrade under temperature extremes. So you use materials that don't. That is what science is for. Vacuum on the other hand has little harmful effect, if anything it strengthens metals.

6. Yeah, a laser pistol would be nice but they are at least 20 years away. You'll see one around 1985 (Actually that was optimistic, I'm writing this in 2016 about 50 years from 1965 and we still don't got no ray-guns).

Sample Weapon Concepts

The images below are from the report, with the title "Possible weapon concepts whose feasibilities have not been determined but are presented as ideas to stimulate thining."

Note the huge triggers and lack of trigger guards, to allow use by a space-suited hand.

Spin Stabilized Micro Gun

Method of Propulsion Propellant 0.0027 lb 0.78 in 0.14 in 3000 to 4000 fps 2 to 4 lb Semiautomatic 30 to 50 18 to 24 in 1.5 in 4 to 6 in

Spin/Fin Stabilized Sausage Gun

Method of Propulsion Propellant 1 to 2 Grains 3000 to 4000 fps 1 lb or less Electrical Semiautomatic 19 to 37 6 to 8 in 1.0 to 1.5 in Spin in VacuumFin in Atmosphere

Sausage Gun #2

Method of Propulsion Gas or Propellant 0.25 in 3000 fps 1 lb or less 19 to 37 6 to 8 in 1.0 to 1.5 in Puncturing of Seal orIgnition of Propellant

Directed Gas Weapon for Close In Fighting

Range 3 to 6 ft Directed Gases fromHigh Explosive Detonation Single Shot orSemiautomatic 1 to 7 1 to 2 lb 4 to 5 in 1.5 in

Spring Propelled Spherical Projectile

Method of Propulsion Compressed Spring 0.20 in 1000 to 1500 fps 3 to 6 lb 20 to 50 18 to 24 in 1.5 in 6 in

Gas Cartridge Gun

Method of Propulsion Gas 0.0012 lb 0.33 in 1000 to 1500 fps 2 lb 25 8 in 0.5 in 3.5 in 2000 psi

Gas Operated Needle Gun

Method of Propulsion Gas 0.0012 lb 0.20 in 1000 to 1500 fps Semiautomatic 25 12 to 16 in 1.5 to 2.0 in 6 in 2000 psi

Ammunition

For conventional sidearms, the ammunition comes in the form of cartridges, which are modular packages containing everything the firearm needs to propel a bullet right into the vitals of the hapless target.

The payload is the bullet, which is the deadly projectile. It is generally composed of something dense to increase its load of lethal kinetic energy inflicted on the target. There are many types. The sub-sections below have details about the more science-fictional types.

The case is the shell holding all the parts together. The metal case also performs a vital role as a heat-sink. Firing a bullet generates a lot of heat, this would make the firearm start to glow dull red except the case carries away the heat as it is ejected (you might have heard the term "hot brass"). The case will have some feature on it like a rim, providing a place for the extractor to grab the case and spit it out of the firing chamber.

This is a problem with caseless ammo, no case means no heat sink. The waste heat is absorbed by the firearm. If the firearm becomes too hot the remaining cartridges explode, which is a bad thing.

The propellant is the charge of chemical explosive (gunpowder, cordite, or something similar) which kicks the bullet down the firearm's barrel and into the target. One of the advantages slugthrowers enjoy over laser pistols is that it is easier to store weapon energy in the form of propellant as compared to an electrical battery. Which is why some SF authors postulate "laser bullets", but I digress.

The primer ignites the propellant. This interfaces with the firearm, generally via a "firing pin." The firearm's firing pin triggers the primer, which lights off the propellant, which shoots the bullet down the barrel and hopefully into the target.

Firearms can generally only use one specific type of cartridge, although occasionally they can accept a slightly longer and more powerful version of the designated cartridge (called a "magnum" round). The reverse is not true: for a given industry- or military-standard size of cartridge there can exists dozens of firearms happy to use it.

Cartridges are packaged in a container called a magazine. This is inserted into the firearm, where it feeds a cartridge into the firing chamber upon request. Occasionally the magazine is an integral part of the firearm, which makes rapid re-loading very difficult. Feeding cartridges one at a time into an integral magazine takes forever compared to ejecting a spent magazine and inserting a fresh one.

To get the real inside scoop on firearm magazines, check out Yoel Mizrachi's in-depth article. It has all the straight dope on both real-world conventional weapon magazines and exotic ones from science fiction.

Yoel Mizrachi has an equally hot companion article on belt-fed ammunition, for all your machine-gun needs. This article also has a nice selection of examples from science fiction.

Caseless Ammo

Caseless ammunition is a firearm round minus the brass cartridge, instead having a sort of solid propellant moulded around the bullet.

Advantages include weight savings allowing more ammo to be carried (about 510 caseless ammo rounds weigh the same as 100 conventional) and not leaving any tell-tale brass cartidges during a black ops mission.

Disadvantages are serious. Caseless ammo requires specialized weapons, they will not work in a conventional firearm. The propellant casing can be easily cracked and ruptured by being dropped or being touched by fingers. This causes misfires, and fragments of cracked propellant are quite difficult to clean out of the weapon.

The most serious disadvantage is thermal. Conventional rounds actually use the spent brass as a heat sink, which is ejected from the weapon. Caseless rounds have no brass, so all the heat stays inside the weapon, overheating it. Eventually the heat causes the entire magazine of caseless ammo to explode in the user's face. This is called "cooking-off".

Future War Storis has a well researched article about caseless ammo.

Frangible Rounds

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.

Flechettes

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.

Explosive Bullets

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:

Smart Bullets

"Smart Bullet" is a general term for a bullet doing something more interesting than just following its trajectory, such as speeding up, slowing down, sending data, etc. More relevant to our interests are bullets that can home in on their target (for increased accuracy or if the target is trying to evade). Some homers require the human operator or a forward observer to paint the target with a laser designator, the bullet homes in on the laser dot. Fancier bullets are self-contained, they are "fire and forget."

In the 1985 movie Runaway the smart bullets were programmed to home in on a specific person's thermal signature. The bullet would merrily chase the victim, dodging other people and following them around corners.

Sandia National Laboratories has announced a bullet that can track a target illuminated with a laser designator.

DARPA's Extreme Accuracy Tasked Ordnance (EXACTO) program has been working on a fire-and-forget system since 2008, they did a test firing in 2014, but no technological details have been released.

Gyrojet

The good old MBA Gyrojet pistol (1968) is worth looking at. This out of production weapon actually fired rocket bullets. The tail jets were angled to spin the rocket bullet in lieu of rifling. Conventional rifling in the barrel cannot be used since rocket bullet does not have enough initial energy.

In Gordon R. Dickson's Dorsai novels, they were called "cone rifles." This was borrowed for the miniature game Space Marines, and from there it spread to the RPGs Space Opera and Paranoia.

If you want all the details, go read the definitive Gyrojet article at Future War Stories.

• It had practically no recoil, about 1/10th a Colt M1911 (but alas, as we saw, recoil isn't a problem in freefall).
• It is more quiet than a conventional firearm. It makes a soft noise comparable to the "pfhsssssssst!" sound of opening a can of carbonated beverage. It does make a "crack" nose when the round goes supersonic; but this happens far in front of the firer, not right at the muzzle.
• The weapon is low mass, since the barrel is never pressurized the firearm can be made out of lightweight alloys or even plastic. The original model was made out of an inexpensive zinc alloy called Zamak. A naive target glancing at a threatening Gyrojet might mistake it for a child's toy, at least until the rockets started flying.
• The firing mechanism has fewer moving parts than a conventional weapon so therefore is less prone to jam. Fewer parts also allows higher firing rates.
• Most of the bullet's propellant is burned during flight outside of the weapon, with much less heat build up. This as well allows higher firing rates, up to 60 RPM.
• Since the precision and high-pressure parts are all in the rocket shell, the weapon itself can be constructed out of low precision die-cast or stamped parts. This also simplifies field repairs. It also has the result of making the weapon relatively inexpensive but the ammunition more expensive.
• The rocket propellant is clean burning leaving little or no residue. Hundreds of rounds can be fired before the weapon requires even minor cleaning.
• The flame of the rocket is only visible from behind, so while the firer can see it the target cannot.
• They work underwater much better than a conventional bullet

Problems included slow burn times. This meant if your target was too close, the bullet didn't have enough time to get up to a speed capable of damaging it. If the target is only 0.3 meters or closer the bullet will probably limply bounce off, fall down, and spin on the ground spitting sparks like a dud firework. The bullet only got up to full speed after it had traveled about 9 meters, which is a bit excessive. Especially considering that average range of a confrontation with a handgun is about 2 meters. At that range a gyrojet round would have a pathetic penetrating power of about 80 joules, about the same as a .22 Rimfire Short cartridge.

For these reason some say the Gyrojet should have been marketed as a long-arm rifle, not as a pistol. The problem could be fixed if a faster burning propellant was subtituted.

The MBA Gyrojet also had poor accuracy. As it turns out, that was due to the MBA ammunition, not because rocket bullets are inherently inaccurate. The MBA ammo suffered from shoddy manufacturing and poor quality control. The main problem was that the bullet's nozzles were not aligned with each other, forcing the rocket off target. The fact that 1% to 10% of MBA's manufactured rockets would misfire didn't help either.

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 missiles, heat-seeking missiles, or smart bullets.

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 pistol had a mass of 0.4 kg (as compared to the Colt M1911 with a mass of 1.1 kg). The over-all length was 27.6 centimeters, with the barrel being 13 cm. The pistol holds six rounds in the magazine, which was regrettably not a removable magazine. The weapon had to be loaded by opening the bolt and feeding rounds into the magazine one-by-one, which made quick reloading impossible.

Gyrojet
Round
ChargeWeightMax VelDmg
13 mm Standard (@2m)2.9 g12.0 g80 j
13 mm Standard (@9m)2.9 g12.0 g380 m/s950 j
13 mm High Velocity7.1 g 7.1 g700 m/s1690 j
13 mm Heavy Weight0.9 g20.1 g120 m/s150 j
13 mm Target0.2 g 7.1 g120 m/s50 j
13 mm Std Long4.5 g17.8 g450 m/s1900 j
20 mm Standard6.5 g43.7 g330 m/s2580 j
Conventional
Round
WeightMax VelDmg
.22 Short 1.9 g340 m/s 80 j
9mm (Luger Parabellum) 7.5 g350 m/s450 j
.45 ACP (Colt M1911)14.9 g260 m/s500 j
.38 Special 9.7 g320 m/s520 j
.357 Magnum10.2 g430 m/s940 j
.44 Magnum (AutoMag)15.6 g450 m/s1560 j

Each .50 caliber rocket "bullet" had a mass of 9 grams (6.65 grams of rocket + 2.5 grams of propellant). The most common rounds were 13mm (0.51 caliber), though others ranged from 2.8mm to 40mm. Each rocket has a low velocity at the point where it exited the muzzle, but by the time it had traveled 9 meters (0.12 seconds after ignition) the propellant had all burnt and the round had accelerated to its full velocity of 380 m/s. The kinetic energy delivered to the target was about 950 joules. By way of comparision a Colt M1911 .45 ACP bullet delivered from 477 to 835 joules and an AutoMag .44 Magnum bullet delivered between 1000 and 2000 joules. However, as previously mentioned, at a range of 2 meters (average range of a confrontation with a handgun) the round would only be fast enough to deliver a disappointing 80 joules.

Effective firing range was about 50 meters. Keep in mind that if the rocket hits something before the propellant is spent, the 5000° F exhaust might ignite the target.

The propellant was a double-based nitrocellulose propellant. These cannot explode, just burn. A composite or metalized propellant was rejected because the magazine would tend to explode if you dropped the weapon or box of ammo. The latter propellants also had toxic and corrosive exhausts, another reason to reject them. The double-based nitrocellulose propellant charge in the round produced a maximum thrust of 33 newtons. The thrust-to-weight ratio was about 284 to 1. The rocket accelerates at something close to 600 gs.

The final advantage of double-based nitrocellulose is that it is smokeless. However, on a cold day the rocket will leave a contrail of condensation.

The angling (port angle) of the rocket exhaust jets is a tricky design task. It divides the rocket thrust into two components: forwards thrust and angled thrust. The forwards thrust propels the bullet towards the target to inflict damage, the angled thrust spins the bullet for gyro-stabilization. The problem is deciding how to divide the thrust between the two components. Too much angled means too little bullet velocity delivering damage to the target. In addition too much angled could spin the bullet too rapidly, causing it to actually disintegrate in midair due to hoop stress. But if too little of the thrust is angled there will be not enough spin for proper gyro-stabilization. Most gyrojet rounds have a port angle of 15°, so 85% of the thrust was in forwards motion and 15% was used for spin. The standard gyrojet round spins at a rate of 3600 revolutions per second (216,000 rpm).

Nowadays designers would probably not bother to use spin gyro-stabilization at all, instead they use smart bullets.

The rocket's case is made of high tensile strength steel to withstand the 17,000 kilopascals internal pressure from the propellant, and the hoop stress of spinning like a top on steroids at 3600 rps. MBA was experimenting with a Gyrojet "shotgun round", where a wad in the nose would hold the pellets, and the wad designed to disintegrate under hoop stress and internal propellant pressure.

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's primer strikes the firing pin, igniting the rocket's propellant. The rocket shoots out the barrel, simultaneously re-cocking the hammer (this steals about 10% of the 13mm std rocket's energy). The hammer is initially cocked by thumbing a lever on the side of the sidearm, in an arc-like groove above the trigger. The cocking lever is on the left side of the weapons, which makes it awkward for left-handed people.

A lip at the top of the walnut handgrip forces the thumb to be straight and low. Otherwise when the trigger is pulled, the cocking lever on the hammer will slam up and injure the hapless user's thumb-tip.

Once the hammer forces the rocket onto the firing pin, it also momentarily restrains the rocket in place. This gives the rocket a chance to "spin up" enough to be gyro-stabilized. Otherwise the rocket would emerge from the barrel unstabilized and accuracy would be impossible.

Unlike conventional designs, the Gyrojet firing mechanism does not need a reciprocating bolt, an extractor, or an ejector. This results in a much lower part count for the firing mechanism, and far fewer ways to jam. The firing mechanism requires no lubrication, and will still operate if the weapon is contaminated with dirt, mud, or other debris.

The weapon's safety switch raises a metal obstruction to cover the firing pin. Unlike a conventional safety, it does not lock the hammer and trigger, which is a rather unreliable solution.

Misfires were a problem as well. You could either manually re-cock the hammer and try again, or open the slide and remove the defective rocket. Be careful opening the slide, the magazine spring will try to eject all the rockets like a jack-in-the-box. Also be careful opening the slide because if the defective rocket is a hangfire, it will suddenly launch into your face (owner's manual recommends a ten second wait). The MBA Gyrojet design could use some improvement.

A gyrojet barrel should be smooth-bore, no rifling is required. MBA put decorative rifling in anyway because of a stupid provision of the 1962 National Firearms Act would have added a tax on the weapons (with no rifling a gyrojet would be classified as Title Two 'Any Other Weapons'). The Mark I gyrojet rounds were 13mm or 0.511 caliber. This would run afoul of the 1968 Gun Control Act, which classifies weapons with a bore diameter greater than 0.50 caliber as "Destructive Devices." MBA responsibly got permission from the BATF to convert unsold 13mm gyrojets into the Mark II version with 12mm rounds, or 0.49 caliber. Later the BATF fixed the problem by classifying gyrojets as "Curios & Relics".

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 (about six dollars a shell in 2015 dollars), with no possibility of re-loading the shells.

There was a a 12mm gyrojet underwater spear gun (called the Lancejet), a snub-nosed survival gyrojet pistol, and an over-and-under derringer modified to accept a gyrojet round in the upper barrel. Like the original gyrojet none of them caught on either. There was also an insane experiment with a "volley gun" variant, which simultaneously fired 12 nine-millimeters rockets with one pull of the trigger.

Bullpups

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.

Looking Futuristic

The firearms in this section are here mostly because they look like something out of a science fiction movie. Indeed, in some cases these weapons commonly appear in low-budget science fiction movies because they happen to look futuristic.

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.

Whitney Wolverine

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.

Beretta U22 Neos

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.

Lone Eagle

Zathras9 brought to my attention another visually impressive firearm: the Magnum Research Lone Eagle.

Cosmo-Dragoon

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.

Rock Island Arsenal Shotgun

This is a compressed air flechette shotgun designed by the Artillery Research Lab in Army Weapons Command in the 50s for use in zero g. According to my source, this was from an Army history newsletter, and had not much info except the photo and the previous sentence.

Apparently this concept laid the groundwork for the Special Purpose Individual Weapon.

Special Purpose Individual Weapon

Apparently the groundwork for this weapon was laid by the Rock Island Arsenal Shotgun.

XM8

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.

Palm Pistol

This section has been moved here

Ludicrous Weapons

Pistol to Carbine

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.

Gauss Rifles

Gauss Rifles are man-usable coil guns, standard coil guns better suited to arm warships with. No, they are not railguns, the explosive arc between the rails would probably instantly kill the weapon user, even if they were wearing powered armor.

Basically coil guns propel their bullets with electromagnets instead of gunpowder.

Future War Stories has a penetrating article about gauss guns.

Most older science fiction fans first encountered these in the role playing game Traveller.

The main problem is that gauss rifles share a problem with laser weapons: they are electricity hogs. They need either a few breakthroughs in battery technology or a very long extension cord.

There also is no clear way to spin the projectile for gyroscopic stabilizing. This is where the word "rifle" comes from, the rifling grooves inside the barrel that force the bullet to spin. But perhaps the coil gun projectile is moving so fast it doesn't need any gyroscopic stabilizing.

Currently there exists no coil gun weapons because nobody can find a good solution to the switching problem.

Triplanetary

This is total space opera without a scrap of real science, but I couldn't resist. In the Lensman series, force-fields can stop ray-gun beams but are worthless as protection against bullets. On the other hand, physical armor can stop bullets but do nothing to stop ray beams. Either protection can be penetrated by an attack of superior force.

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