What is the purpose for the rotating gun barrels on a gattling gun?
My guess is to reduce heat so that you can fire faster, but in some applications (such as fighters like the warthog) it seems as though the barrel is powered and rotating really fast - how could the barrel cool down enough in one rotation?
http://www-acala1.ria.army.mil/LC/cs/csa/aagatlin.htm#M61
More bullets, less damage to the gun (than recoil/gas/etc.-driven fully automatic machine guns).
1000-1200 rounds per minute seems to be pretty close to the maximum rate at which you can push projectiles through a barrel, in short bursts, without destroying the barrel. Now, at the speeds jet fighters fly, they can litterally fly right between the projectiles at that speed. Your choices are to either put more weapons on the platform, or make the weapon that’s there fire faster. Can’t fire one barrel faster without having to replace it frequently (not to mention dealing with having to design an action that’s fast enough!)… Put more barrels on the weapon! Dr. Gatling came up with a nice practical sollution for that, let’s dust it off!
Modern fighter weapons don’t fire continuously, they fire in relatively short bursts, so they only need to avoid stripping the barrel for short times, and cool off between bursts.
The Russians had a nifty cannon that did this a little differently: One weapon with two reciprocating actions, two barrels. The recoil of one action would cock the other action, giving a very high rate of fire for a very simple and robust design. Nowadays, they also use rotary barreled weapons.
With a single barrel automatic weapon, there is a limitation caused by the length of the barrel itself. Until the expanding gasses which propel the first projectile are allowed to escape, the second bullet cannot be reliably fired, because the second bullet must fight the back-pressure from the first. The Gatling process theoretically allows you to put projectiles into the air which are spaced very near to or perhaps even less than the length of the barrel, improving rate of fire to near firehose levels.
It’s not the only way to do it, but the Gatling process does have some fringe benefits such as built-in air cooling. That helps some, but I’ll bet you can melt a Gatling in short order just as you can wreck most other weapons with a high rate of fire by keeping a finger on the trigger for too long.
At the extremes of modern automatic weapon fire, the probability of melting down a multibarrel machine cannon are fairly well overwhelmed by the probability of running out of ammunition. Sustained automatic fire goes through more ammo than you can carry in fairly short order. (6000 rounds in a minute, remember?) Considering that you are flying around with bombs, and missiles and pilots and such, as well, there isn’t room for that many thousands of rounds on board a fighter. Besides, what the hell are you shootin’ at, you need to hit it 12000 times? Did you Miss?
Now, sitting on a test range with a truck handy, you probably could do it.
“You could park a car in the shadow of his ass.” ~ Geena Davis, in Thelma and Louise ~
You should check out the link Sofa King provided. Someone (maybe Sofa King…I don’t remember) posted that awhile back and I’ve had the video of that gun on my PC ever since. 6,000 rounds/minute is nuthin to the Metal Storm. What do you think about 30,000 rounds/minute? Sounds crazy huh? I guess 60,000 rounds/minute would be ridiculous. 1,000,000 rounds/minute would be downright ludicrous. Believe it or not however the Metal Storm pulls it off (of course the 1,000,000 round/minute shot was done with only 180 bullets…the firing rate is then extrapolated). What would be the practical use of such a thing (i.e. some use that benefits from putting 1,000,000 shells per minute on target rather than ‘only’ 6,000)? I have no idea but it’s pretty amazing nonetheless.
You don’t have to melt a barrel to destoy it, simply get it hot enough to damage the rifling, or cause distortion. At 1200 RPM, that happens in very short order, even with modern metalurgy. Just lean on the trigger too long, that’s all it takes…
MetalStorm uses many barrels, so the rates of fire per barrel are actualy fairly low. It was featured in another thread, where I discussed it to some degree, here.
The Gatling gun type principle is that as the gun assenbly turns, a camming action at the bottom performs the essential functions of loading, closing the breech, firing, and extracting the spent shell casing. In other words, if you could see a very high speed photograph of such a weapon being fired from various viewpoints, you’d see that while one barrel (say at 12 o’clock) is firing, the one at 6 is ejecting the spent case, the one at 9 is loading, and the one at 3 is opening after firing.
Note that with a multi-barrel weapon all of these actions can be taking place at one exact moment instead of in sequence, as would be the case with a single-barrel weapon.
This permits the very high rates of fire needed for high speed aircraft. The USMC’s AH-1 helicopter, being a bit slower than (say) an F-18 only needs (and uses) a 3 barrel 20mm cannon.
Tranquilis, the US at one time had a 2 barrel gun such as you describe. I forget the designation, but I had to read the manual once and be up on how it worked, though I never saw one in person. It would fire the upper barrel, both barrels, then the lower barrel. I think it was a 1950’s design.
I beleive now the Europeans favor a revolver cannon for aircraft. It works like a cross between the gatling gn and a revolver pistol. It has the rotating action like the gatling for fast feed, but only has one barrel that remains fixed. Supposedly this saves weight and makes it easier to install and maintain.
In reality, most such aircraft cannon are now only used against ground targets. The Vietnam War and the 1967 mideast war made designers want to go back to the gun on aircraft after finding out that the missile didn’t do as well as envisioned in the hard dogfighting that took place. This was a function of two things: the then state of the art in electonics, and the environment in which the combats took place. IIRC, they found that something like 70-80% of all “kills” in the 1967 war were “gun kills” vice missile. But the state of the art in electronics and tactics improved quickly, and IIRC the 1973 “Yom Kippur” war more than reversed that ratio, then the 1982 (?) Lebanon war and the 1991 Gulf War turned it to 100% missiles 0% guns (though in the Gulf, an A-10 did get a helicopter with his 30mm monster gun —but I don’t count it here as it wasn’t a fixed-wing vs. fixed-wing fight).
I have a question or 2…
Is the barrel continusly rotating at a constant speed or does it stop/fire/start/stop/fire/start (when firing)?
Does the barrel rotate while the round is still traveling down the barrel? - If so how does this effect accuracy?
It’s a continuous rotation, and yes, the bullet is in the barrel while the barel is rotating, and it does affect the Point-of-Impact. The weapon is simply mounted and adjusted such that the actual point of impact of the projectile at a certain distance alligns with the sights. Called “Synchronization”, I believe.
If you watch the show “Mail Call” on the History Channel, their very first show showed this effect quite handily: The faster the gunner cranked the barrels of the Gattling gun, the more the point of impact shifted on the target. Modern weapons are constant-rotation, so you don’t have to worry about wandering points-of-impact.
Just what sort of monster truck is this metal storm million round a minute gun being designed for? Melting down your gunbarrell is not the only design consideration.
Assuming the smallest reasonable round, we are talking of truckloads of ammo per three second burst. If you want to actually fire something hefty at it, you need to mount it on a rail car, just to hold the ammo. (the main drawback of the wonderful new Crusader artillery system is that it is just too darned big, with the amount of ammo it needs, to be useful in most combat scenarios.)
And again, what the hell are you shootin’ at, you need to hit a million times?
Tris
Oh, it’s not that bad, Tris. Metal Storm uses sequentially-loaded barrels, 20 or more bullets in a single barrel, which are fired electronically. They then gang several hundred barrels together in a bundle, creating what is essentially a giant ‘volley gun’. The ‘million rpm’ shot was actually only 180 rounds fired at a rate of one million rounds per minute. It sounds like one ‘bang’, but is infinately varriable in ROF, as they can set the electronics to fire at pretty much whatever rate you want. It might be useful in CIWS-type situations, ot on expendable weapons platforms, or in space, or in survival/emergency stores kits. Can’t think of much else use for it, IRL.
Hmmmmmm
Field of fire saturation for high speed ballistic targets, maybe. Or other such applications where you don’t have time to detonate a shrapnel round. That looks like a fairly narrow combat parameter for something that has to be a bear to maintain.
But a single burst of 180 rounds seems to imply that there is some reason why they didn’t fire off a couple of thousand, or better yet twenty or thirty thousand, just to impress the weapons acquisition guys. This thing sounds to me like a boondoggle waiting for a budget surplus.
Tris
Essentially correct. It’s a solution looking for a problem, a nifty piece of ‘gee-whiz’, but not much more than that at this point.
trivia:
not all firearms that are called gatling guns rotate: there are kits for mounting two or more ordinary semiauto rifles on a tripod with a hand-crank mechanism which uses cams to push the triggers alternately. Since it still “fires one round per motion of the trigger” it’s not considered an automatic weapon.
A friend of mine owns one of these made of two 10/22’s. Extremely cool looking toy, but its difficult to get sighted in, and full capacity mags for 10/22’s vary widely in quality, so he doesn’t shoot it much anymore.
Sorry to pick on you Tranq, but
This line is haunting me. I keep thinking of some GI cook, looking at the elephant that some private killed with his emergency metal storm gun. “Gee, Sarge, can you make hamburgers out of what’s left?”
Tris
I don’t have a cite handy, but way back when I first read about the Metal Storm, I heard it had some sort of portential as a minefield-clearing application. Didn’t make sense to me then, and doesn’t now, just thought I’d point it out.
The last tidbit about the Gatling-concept weapon that no one’s brought up yet is that it’s electrically driven.
In other words, it’s no longer ammunition-dependent. In nearly all other “machine” guns of the time, the gun itself is cycled by the firing of the previous round, either by simple blowback, or short-recoil, or gas operation. But if you got a dud round in the belt, the gun stopped until that round could be cleared.
And for wing-mounted machine guns in flight, such a stoppage was near-fatal; that gun couldn’t be cleared and made working again until you were back on the ground.
With the electric operation and independent breech mechanisms, if a round failed to fire for whatever reason, the system continues to cycle normally and just dumps the unfired dud overboard as if it were an empty.
Of course, later other guns were converted to electric drives, and other electrically-operated “chain” guns (motor drives a short loop of chain, the chain cycles the breechblock which does all the feeding, locking and extracting) were developed, but that the time, taking the ammo dependence out of the equation was actually rather noteworthy.
I think I may not have grasped this correctly, but if a round misfires, wouldn’t it still be in the breech section and not the barrel? (and therefore still cause a jam?)