Could rotary (Gatling) type guns have been carried by WWII aircraft?

[Exhausted]

I've been wondering why gatling gun development stopped before WWI only to reappear after WWII.

If rotary machine guns had been around during WWII, would aircraft have even been able to use them? I'm no expert, but I'm assuming that bleed air from jet compressors works to pneumatically drive modern cannon like the M61. If this was the case, I think that a supercharger-like device could probably provide the same power. Also, what would the weight trade off be like for an American fighter like the P-51 or P-38? Maybe the removal of 6 MGs and their mounts would offset the weight of a rotary gun system.

I can just imagine what a single 0.50 cal rotary gun could do to anything it's aimed at. A single weapon mounted through the prop hub of a P-51 or the nose of a P-38 would have been amazing. Also, bomber turrets would have been deadlier. But like I said, would it have been possible?

[ikar]

The Vulcan is a big, heavy weapon. I can't see a WWII fighter carrying that much weight and still be viable as a fighter, assuming it could get off the ground. As far as I know, all other gattling guns work with an electric motor to spin the barrels.

H\What do you think would be the rate of fire with something like a 50 cal?

You would probably have ot go with a 30 cal weapon and turn down the gun's speed so it would not slow the aircraft too much. Then, how much ammo could you actually carry and feed reliably to make it practical?

[Exhausted]

Would a 0.30 cal firing at 60rnds/sec done the job in most cases? Probably, but not as much as a 20mm.

As far as weight is concerned, that doesn't seem to be a problem. One M3 0.50 cal weighs about 80 lbs, which is 480+ lbs when you put six of them together. The M134 of 1960 weighs 85 lbs. An M61 weighs 248 (according the wiki) without the feed system. But every practical weapon system has a feed system that weighs extra so this may not be a stretch. My guess is you'd only need 1 of them in most cases.

In a VERY extreme what if example, a P-51 could have some of its fuel moved to the wings in place of the M3 batteries. The new space could house a M134 size weapon which would fire through the hub.

Edited July 19, 2015 by Exhausted

[Smokey]

Feasible or not, it sounds like a fantastic wiff,

B-17 gunship, miniguns in the chin, and waist, tail with a minigun above the .50's, top turret still with twin 50's and a second ball turret around the bomb bay...

The big question is - do I have the ball turrets to do it in 1/32????

[spejic]

The gun would then move forward of the center of gravity so you would need to redesign the aircraft. But the bigger problem is that in other aircraft with cannon shooting through the airscrew shaft the cannon barrel is inside that shaft. You can't do that with a multi-barrel gun because there isn't enough room in there for multiple barrels, and that space is limited by the engine itself so it can't be expanded. You can either have the whole cannon between the engine and the pilot, so the pilot would be moved back like in a Bee Gee racer, or you can have an Airacobra-style arrangement with the engine behind the pilot (but you still need more space in the front than the P-39 has).

And you need to vent those gasses somehow.

[toadwbg]

I wonder how much of an issue arises from vibration of a rotary cannon? I would think worst-case you might shake a prop plane of the era apart and/or conflict with the resonance freqency of a radial or in-line engine.

I'm no expert in vibration engineering, but I work with some. Vibration was not a well-developed science by the war. Since that time, modeling and similation has come a long way.

[fulcrum1]

[Horrido]

I've often wondered what you could do with a P-38 modified with turbo-props, a .50 GAU-19, and a gunnery radar/computer/sight and HUD.

A GAU-19 should be able to fit within a wing of a nose-engined fighter.

Biggest challenge would be ammunition conservation.

Edit:

Edited July 19, 2015 by Horrido

[Exhausted]

Maybe ammunition conservation would look like an issue, but the weight gained by deleting 5 MGs and sticking with one is nearly -400 lbs on a P-51. 400lbs is quite a bit of ammo. Or you can go with less ammo and have a faster plane that can catch up to the late-war Luftwaffe planes and waist less ammo shooting them down.

[Aaronw]

M134 would have been useless by 1942. There is a reason most nations got rid of their ".30 cals", early in the war, they were all but useless once aircraft started to get more armor. At the start of the war the British favored lots of .303 Brownings (up to 12 in the Hurricane for a combined ROF of 14,400 rpm or more than double the M134), they quickly (by 1941) dumped this weapon set up for 20mm cannon.

The Germans similarly started off in Spain with mostly 7.9mm mgs, but had gone to mostly cannon armed by 1940. Same with Japan (7.7mm) and the USSR (7.62mm) all of whom adopted 20mm armament in some form.

There were examples of American aircraft being fired on by German and Japanese aircraft that had run out of their cannon ammo and were trying to finish off heavily damaged aircraft with their rifle caliber machineguns with no effect.

The USA was the odd ball with the .50 cal, so maybe something like the .50 GAU-19 but that isn't getting you anything (max of 2000 rpm for the GAU-19 vs 2400 rpm for 3x .50 M2) except for possibly a more compact weapon, but one that has to have room for a large gun vs distributed where they fit best. The Korean War Era .50 M3 increased the ROF to 1200 rpm, so you would need 4 GAU-19s to surpass the firepower of the F-86 Sabre with gatling style weapons. The GAU-19 would only save about 100lbs vs the 6 gun M2 armament (6x 61 lbs vs 2x 139 lbs).

The Germans had 20mm and 30mm revolver cannons developed by the end of the war which post war led to the adoption of similar designs by the USA, Britain and France.

Jets have big empty noses so a big gun right up front works fine, most WW2 fighters had a big engine in the nose, so you would have to put the guns in big wing mounted pods.

M61 Vulcan in a P-38 might be interesting, although I doubt it would be an easy conversion, and ammo consumption would probably be a serious issue, it would only have about 15 seconds of ammo.

Edited July 19, 2015 by Aaronw

[toadwbg]

I was thinking of that too, or an AC-130 gunship. These guns as shown I can see working out as they are not mounted directly to the frame, wings, or engine mount. This is also a fairly large plane compared to a fighter aircraft like a Mustang.

[Grey Ghost 531]

The point of the Vulcan was the need for a high rate of fire to allow enough metal to be on target during the fleeting instant the sights were on the target in high speed jet combat. Back in WWI, the airframes were vastly more delicate than a modern ('50s modern when the Vulcan came out) supersonic jet, plus they were a lot slower so the relative speed difference between the attacker and the attacked was much less so one or two rifle caliber machine guns were sufficient for the job.

Korea showed that rifle caliber machine guns often didn't succeed against high speed, thick skinned jets. The Navy figured it out quicker that 20mm cannon worked better, but four of those had a hard time hitting a fast jet enough times to kill when the sights could only be on target for fractions of a second at a time. So, the Vulcan was designed to put out 100 rounds in a one second burst.

I don't think a DH-2 or the like could have carried enough ammo to feed a Vulcan-like weapon.

[Exhausted]

Thanks Ghost, but I definitely didn't say that any WWI plane was a candidate, only certain WW2 birds were.

[dmk0210]

M61 Vulcan in a P-38 might be interesting, although I doubt it would be an easy conversion, and ammo consumption would probably be a serious issue, it would only have about 15 seconds of ammo.

I think the P-38, B-25 (gun nose strafer) and Mosquito were the aircraft that this might have been feasible in assuming that the engineering problems of the gun itself were worked out.

The p-38 had a 20mm plus four .50s in the nose. Replace all those with an M-61 Vulcan and they could have had a streamlined pod under the fuselage to carry the ammo.

The B-25H probably could have carried a 30mm Gau-8. They actually put a 75mm howitzer in those. That Gau-8 would have done a job on ships, even warships!

Edited July 19, 2015 by dmk0210

[TaiidanTomcat]

Even the A-10 can stall if it fires for too long a burst.

[Aaronw]

I think the GAU-8 has technological issues beyond the gun, the ammo plays a major part and is well beyond the known technology of the 1940s.

Something else to consider with a B25, the strafers with gun packs had 14-18 forward firing .50 cals (a ROF of 11,200 - 14,400 rpm), so you are back to multiple M61s, a single gun in the nose drastically reducing ROF. Although for strafing M134 miniguns would be a possibility which could result in an insane number of bullets downrange.

I think something being overlooked is the aircraft guns of WW2 were the peak of "standard" configuration weapons, the post war rotary cannons were built to solve a problem the WW2 aircraft had not yet discovered. These were not warmed over WW1 aircraft guns. In fact I would even think perhaps the rotary guns were a response to guns becoming secondary air to air weapons.

Several WW2 era ground MGs are still in service largely unchanged, MG3 (just a WW2 MG42 in 7.62mm NATO), and M2HB (82 years of service to date with only minor modification) being two well known examples, so they obviously got something right.

The Soviets had several revolver guns in service during WW2, the 7.62mm ShKAS (introduced in the 1930s), had a rate of fire of 1800 rpm and weighed only 10.5kg. An M134 minigun has a ROF of 6000rpm and weighs 39kg. Four ShKAS weighs only 3kg (6.6lbs) more and offers a 20% increase in the ROF (7200rpm), assuming the M134 could have been built to its modern weight in the 1940s (unlikely).

Edited July 19, 2015 by Aaronw

[Exhausted]

Well flight limitations didn't begin with the rotary cannons of the Cold War. Pilots have always adapted to their weapon systems, beginning before WWI. The M2 will jam when pulling gs in some mounts (P-51B but not P-51D), all will tend to overheat when sustaining fire for long periods, and it seems all of the major powers experimented with oversized cannons: 57mm in the Mossie, 75 in the Mitchel, 75 in the Ju-88, 50 in the Me-262, 40 in the Shoki, 40 in the Yak-9, etc.

I have no doubts that if the gatling weapons weren't dropped in 1911, aerial warfare would have adopted them and history would be a bit different.

[Aaronw]

I don't think a DH-2 or the like could have carried enough ammo to feed a Vulcan-like weapon.

The complete M61 Vulcan installation in most fighters weighs almost as much as a DH-2. :D

[Aaronw]

Well flight limitations didn't begin with the rotary cannons of the Cold War. Pilots have always adapted to their weapon systems, beginning before WWI. The M2 will jam when pulling gs in some mounts (P-51B but not P-51D), all will tend to overheat when sustaining fire for long periods, and it seems all of the major powers experimented with oversized cannons: 57mm in the Mossie, 75 in the Mitchel, 75 in the Ju-88, 50 in the Me-262, 40 in the Shoki, 40 in the Yak-9, etc.

I have no doubts that if the gatling weapons weren't dropped in 1911, aerial warfare would have adopted them and history would be a bit different.

I think you are being rather US-centric, note that most other nations have opted for revolver over rotary designs for their aircraft guns. The US has also typically chosen smaller caliber higher velocity rounds, while Europe has preferred a larger caliber. WW2 .50 vs 20mm / 30mm, Post war 20mm vs 27mm / 30mm.

[Exhausted]

The reason I come off as being US-centric is that I really don't know how revolver/rotary cannons like the DEFA and GSH-30-1 work. My personal experience with these weapons is limited to a visit to a MALS ordinance shop that dry-fired (?) a GAU-12/U. Also, i wrote a post that didn't make it due to a browser error highlighting many other possible candidates from the 5 biggest players to carry these weapons.

I think that, in some cases, the weight savings would make a fighter fast enough to close with enemy aircraft to a very short distance and also give it a higher thrust/weight ratio needed to stay on a bandit's tail.

Would the Battle of Britain have looked different if Spitfire Ias made it to altitude faster and sprayed a concentrated grouping at German bombers, as opposed to using 8 mgs that fail to converge at various rangers? Could .30 cal rounds coming out of a single m134 have done more damage than .303 rounds coming from 8 MGs all hitting various parts of the bomber?

Edited July 19, 2015 by Exhausted

[toadwbg]

The reason I come off as being US-centric is that I really don't know how revolver/rotary cannons like the DEFA and GSH-30-1 work. My personal experience with these weapons is limited to a visit to a MALS ordinance shop that dry-fired (?) a GAU-12/U. Also, i wrote a post that didn't make it due to a browser error highlighting many other possible candidates from the 5 biggest players to carry these weapons.

I think that, in some cases, the weight savings would make a fighter fast enough to close with enemy aircraft to a very short distance and also give it a higher thrust/weight ratio needed to stay on a bandit's tail.

Would the Battle of Britain have looked different if Spitfire Ias made it to altitude faster and sprayed a concentrated grouping at German bombers, as opposed to using 8 mgs that fail to converge at various rangers? Could .30 cal rounds coming out of a single m134 have done more damage than .303 rounds coming from 8 MGs all hitting various parts of the bomber?

Shotgun/scatter-gun effect? Several guns offer redundancy as well as a larger effective area.

[Exhausted]

Yeah, I acknowledge the scatter effect that rotary cannons have, but 15 mils (for example) would still be 15 mils at 100 yards, or 1000. With a Spitfire you have 8 wing mounted .303s, all outside of the prop disc. If you're zeroed for 200 yards, you get too much scatter at 50, and then you get even more at 500. The M134 wouldn't have the same problem.

[Aaronw]

Revolver guns work like a revolver handgun, except they can load during the operation unlike the small arms. Similar idea to the rotary gun, both having multiple chambers but the revolver gun only has a single barrel.

Rotary cannons are better for sustained firing (more barrels to absorb heat), but the revolver gun is less complex with no requirement for an outside power source. A rotary cannon can be sustained by gas operation, but still requires power to get it going. I found one quote of 35hp or 25kW required to spin the M61.

A revolver cannon gets up to speed instantly since it just has to spin the chambers, not the whole mass of barrels. The M61 takes about a 1/4 second to get going, which isn't much but if you are only doing 1/2 to 1 second bursts, a 1/4 second is a measurable amount of time. It makes a 1/2 second burst from an F14 (M61) more or less the same as a 1/2 second burst from an F5 (armed with 2x 20mm M39).

The most apples to apples comparison between a revolver cannon and rotary cannon would be the US 20mm M39 used in several 1950s aircraft, 1500rpm, 178lbs and uses the same ammo.

The M61 is hard to pin down on weight, the 248lbs often quoted is not for the complete weapon which may actually weigh several hundred pounds more when installed with its required hardware, power supply (electric or hydraulic), feeding mechanism etc. The fact they could shave more than 40lbs off the A2 model used on the F22 just by using thinner barrels gives some indication of how much those 6 barrels actually weigh.

Not saying the M61 is a bad weapon, there is lots of wreckage out there that proves it works. Lots of wreckage caused by single barrel guns too. It is no doubt superior for something like the AC130 where 2-4 second bursts may be more common, but far less advantage in fighter armament.

[dmk0210]

Well flight limitations didn't begin with the rotary cannons of the Cold War. Pilots have always adapted to their weapon systems, beginning before WWI. The M2 will jam when pulling gs in some mounts (P-51B but not P-51D)...

The M2 itself didn't require any fixes for the jamming issue in the P-51B, it was the aircraft's ammunition magazine that caused the jam. The feed chutes were redesigned in the P-51D and that fixed the problems.

Almost all the US fighters in WWII had M2s and didn't have widespread problems with jams when pulling Gs. (guns sometimes did get misfeeds and jam of course, but it wasn't a chronic problem like the P-51B)

BTW, the F8U Crusader had a similar problem with its 20mm guns jamming due to feed issues in high G maneuvering.

Edited July 21, 2015 by dmk0210

[dmk0210]

Would the Battle of Britain have looked different if Spitfire Ias made it to altitude faster and sprayed a concentrated grouping at German bombers, as opposed to using 8 mgs that fail to converge at various rangers? Could .30 cal rounds coming out of a single m134 have done more damage than .303 rounds coming from 8 MGs all hitting various parts of the bomber?

Shotgun/scatter-gun effect? Several guns offer redundancy as well as a larger effective area.

This raises a good point. Modern guns are radar aimed and use a computer to calculate optimum trajectories. The sight systems in WWII were relatively rudimentary in comparison (though they did have more advanced computational sights towards the end of the war).

On the other hand, P-38 aces have stated that they did like the fact that all the firepower in that aircraft was concentrated at a single point on the centerline rather than spread out of the wings like most fighters.