All will, at least once. It can be very bad to do so, as the gun may blow up. I'd expect an SMG/AR to blow up with water in the barrel.

For example:
http://www.glockfaq.com/generalinfo.htm
The Glock 17 may be equipped with an optional set of maritime spring cups for use in water environments. Maritime spring cups are not intended for submerged firing, but for surface use by special ops teams who operate in and around water. The maritime spring cups are two small parts within the firing pin assembly and are not included on any Model 17 sold by Glock (civilians can only get them through 3rd parties). They insure that water can pass by the firing pin within the firing pin channel, thus preventing the creation of hydraulic force within the firing pin channel -- which would slow the firing pin down, causing light primer strikes. With the special cups, the action will cycle reliably while submersed, if a little bit slower. NATO specification ammunition (such as Winchester's Ranger RA9124N) with waterproof sealed primers and case mouths is recommended.

Although you may install the maritime spring cups on any Glock model, *only* the Glock 17 was designed and intended to use the modified spring cups for aquatic firing -- and only then using 9mm ball ammunition to remain within acceptable pressure limits. The foolhardy who insist on living dangerously must keep several things in mind: The Glock 17 must be fully submersed underwater. There must not be any air left within the pistol as the muzzle is pointed towards the surface of the water after submersion to allow the air in the barrel to escape. Use only full metal jacket, ball-type ammunition because the water within the barrel can spread a hollow point out within the barrel upon firing. This increases the bearing surface of the bullet to the barrel and could catastrophically increase pressures. Even if the barrel doesn't burst, the expanded bullet would get even bigger upon exiting into the water and would slow down very quickly while tumbling. Accuracy would be terrible.

The marinized Glock 17 is primarily for use by various Special Warfare units operating in aquatic environments. At least one specialized Scuba diving group regularly uses G17's to dispatch sharks where they dive. The Glock 17 using NATO specification ball ammunition will completely penetrate a minimum of one 1/2" pine board at a distance of ten feet from the muzzle when fired underwater.

Trained personnel who use Glocks underwater know they must obey several rules:
1) use only a Glock Model 17 with amphibious spring cups (reliability issue);
2) use only 9mm FMJ subsonic, sealed primer ammo;
3) completely immerse the pistol and get *all* the air out of the barrel;
4) wear protective ear plugs, gloves, wet suit, face mask, etc.;
5) do not fire near solid objects or in enclosed spaces to prevent return
concussion.

However, any Glock -- even those not equipped with maritime spring cups -- will normally fire while submersed underwater. But doing so may generate excessive internal pressure and may cause the pistol to literally blow up. This is especially true with the use of high-pressure rounds (such as the .40 S&W/357 SIG) or hollow-point bullets.

I recall a reported incident where a Glockster on a boating holiday decided to show some friends how his Glock would fire underwater (because Tommy Lee Jones said so in the movies). He stuck his hand overboard, pulled the trigger and came back with a bunch of shredded plastic and a badly injured hand.

Another reported case was the Glockster who decided to try out his Glock 23 .40 S&W in the swimming pool after seeing pictures of Glocks being fired underwater on the web. He was totally submerged, with the gun, as he fired at a piece of wood on the bottom of his pool. The Glock did fire, the .40 S&W FMJ round left the barrel and went into the wood. The chamber also exploded and implanted shrapnel into his leg. Thinking that the water would muffle the blast, he did not wear hearing protection (the blast is actually about 4 times louder underwater). He is now mostly deaf in one ear and hears high-pitched tones most of his waking life.

Does your stuff work in the rain? If so it will probably work in water, at least until you are totally swimming.

In the real world, very little electronics is certified for use below 10 feet or so unless it's built for diving. So I'd guess that typical equipment wouldn't work so well if you took it wreck diving to 50 meters of sea water. Buy (and pay the big bucks for) milspec stuff built for SEAL teams if you want to do things like that.

It did get deployed with some German elite units, the German goverment bought like 3000 of the 12 million or so that were in the contract. (East German reunification cancelled the deal.) Mixed reports is what I heard. Not in use any more.

The G11 rifle also had a complex action IIRC, with really tight tolerances.

WHAT?!

the one I can thing of is the Colt Water Carbine. SMG if I remember correctly.


Guns dont work well underwater, or at least in my games. The "water carbine" is designed to work underwater are your only options.

in RL, guns do work underwater but the range is nada. But this is a game so I allow the "water" guns to actually works.

The minimum is that they are modified so that the firing pin doesn't get too slowed down by the water. And the round chamber pressure with water in the barrel is less than the bursting pressure of the weapon plus the safety factor.

The USSR designed some special purpose weapons explicity designed to work underwater. They are still for sale from Russia as far as I know.

The SPP-1 underwater pistol, 4 barrel firing darts ,effective range 11-17 meters, dart doesn't stabilize in air.
http://world.guns.ru/handguns/hg140-e.htm

APS underwater assault rifle, 20or26 round mag, selective fire, 10-30 meter effective range in water (depth dependent), apparently not good in air, cyclic 350-600 RPM (depth dependent). Also fires darts.
http://world.guns.ru/assault/as69-e.htm

You really should check it out if you get the chance. They used a variety of weapons, from pistols to rilfes, shotguns to (IIRC) a machine gun of some type. (It's been a while, and I was only half paying attention at the time )

The faster a bullet is mooving when it hits the water, the greater the deceleration forces it experiences when it hits the water. Drag (the force exerted by a fluid on an object moving through it) increases as the SQUARE of velocity (aproximately). For a bullet moving relitively "slowly" this force only deforms the bullet slightly, and it continues on it's way for a few feet, though not in a straight path most of the dime due to the defformation of the round). A bullet fired twice as fast will experience about 4 times the force (per unit of surface area) and be shredded into numerous lower-mass fragments which are not aero (or, more relevently hydeo) dynamicly efficent. This makes the .50 BMG/FMJ round berak apart within INCHES of strikeing the water. Beyond a few feet the fragments will have lost the velocity required to cause serious injury. Additionaly, the shreded pieces will corkscrew off in every direction.

To answer your query: No. They used standard (as I recall) FMJ rounds, appropriate to the weapon in question. It would be hard to find a 9mm pistol round with the same mass as a .50BMG round or vice versa. The 9mm would need to be made of depleated Uranium or some one super-heavy metal, or the .50BMG woudl need to be made of Aluminum. Either of these changes woudl result in dramaticly effecting the balistic properties of the round. In the case of a super-heavy 9mm, it could even destry the weapon by dramaticly increaseing cylinder pressure.

The final conclusion was that by diving down five or six feet, you could be completely protected from people fireing from the surface.

APDS would almost certainly destroy the weapon, as the high velocity = high pressure, which means the sabot would probably break apart in the barrel, with the penetrator exiting the side of the barrel.

Personally...

Most Guns in 2070 (Semi-Autos and Automatics):
Roll 1d6 for every bullet in an attack (or 1 per attack, for single-shot). If any die is not a hit, the water disrupts the gun's ability to cycle itself, causing a jam.

Manual Action (Revolvers, Pump-action shotguns, etc):
Roll 1d6 for every clip. If any die does not come up as a hit, some random bit in the gun has suffered damage, making the weapon inoperative. Note that these guns, with the exception of the Ruger Super Warhawk, appear to be archaic by 2070 (going by the SR4 gear section).

Guns Specifically Designed to Fire Underwater:
Yay, you planned ahead! No penalty.

So you're saying any shot -- even the first -- only has a one in three chance of going off?

Once you start messing with ROF and speed of the slide all sorts of weird stuff, none of it good, often starts to happen to automatic weapons. They are a carefully tuned system, and messing with a part a little bit can result in bad things. This is why Stoner didn't approve the use of ball powder in M16s, and why it caused them to malfunction like mad.

Hmm, then should the Yamaha Sabura Fabuki work underwater?

Everyone,

Thanks for the great replies so far. In what way should I offer my players guns that work underwater? Should it be a mod to existing guns, specific specially designed guns, or both? How much should it cost?

Special guns. I'd steal either the HK or the soviet ones. They'd have high availability for both the gun, mags AND the ammo, and they would all be expensive. If available at all. The HK "Return to factory" reloading would proably be $250 - 500 (HK is never cheap) and a week - you do have a permit, right?. The Russian stuff probably $10 per round for the pistol, $15 per round for the AR ammo, $75 for the magazines, 3x cost of the predator for the pistol, 3x AK97 for the AR. HK pistol I'd probably price base at $2000.

Remember the crappy performance in the air from all of these. I'd give an availablity of 15r (or f), as they are just not common.

Couldn't find the video (episodes 34 (second season) and 51 (third season) are the relevant ones), but here's a link to the results of the tests. The 9mm was a SIG P239 and the .223 rifle was a 16" AR15, IIRC. What's listed as an "M1 Carbine" in this article was actually an M1 Garand. The .50 cal was an Armalite AR-50, and the shotgun was some single-barrel break-action I'm not sure of.

Here's a link to the results of the second test they did.

Not that I know of. The bullet would encounter more resistance in tissue or gelatin, which should cause it to fragment faster.

As for the other questions, as water provides more resistance against moving parts than air (the gaseous environment in which most firearms are designed to operate), those parts are not going to operate as designed. Semi-automatic firearms are very likely to malfunction when fired underwater. An MP5 is definitely going to malfunction, it's just a question of how long it takes (I would guess sooner rather than later, even firing semi-auto). The biggest problem is in ejecting the spend cartridge case and replacing it with a new one. As the bolt's velocity is reduced, so is the amount of force applied to the case head as it is pushed out of the gun. Also, the case itself has to overcome more resistance. As such, cases tend to "stovepipe" jam (i.e. get caught sideways between the bolt and breech face, leaving the case protruding from the ejection port). So removing the case or the need to eject it are generally the first problems to be tackled.

As for whether Shadowrun's firearms would be significantly different from those of today, I would say no. Unless a firearm is specifically designed to fire underwater (and a few have been), they're unlikely to be much different. As far as the art of pushing little bits of metal out of tubes goes, we've pretty much maximized the economy of it all. Other than things like cymbernetic integration (which is pretty much going to require electronic primer ignition, which is obviously going to be problematic underwater) and making propellants take up less space, I don't think there's going to be much change so long as the objective is to hit something at a distance with a bullet.