Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

I think you hit a number of the key issues. One is certainly weight, of guns, ammunition and the structure to support the guns and the belts. IIRC Hurricanes had a truss type wing construction, with spars and ribs made of thin rod-like elements, while the Spitfire had a stressed skin construction, with stamped ribs and the spar being a mix of stretched sheet metal, extrusions and machinings. In general, a sheet metal structure will give you more choice in where you add new structural elements, which makes (again in general) for lighter structure.

The sheet metal construction will also give you more choice in where you place new items like cannon (easier to make cutouts, more choice in structural design of attachments, more open space), and therefore might have made it easier to stagger the guns and permit longer belts.

Also, you would need to know where the "other bits" are inside the wings. Studying the cutaway drawings on the Flight website might explain differences in the relative gun positions within the wings. I think both Hurricane and Spitfire cannon installations were done fairly quickly, so they would not have been interested in re-designing and requalifying flight control push rods and cable runs, fuel tanks, and whatever else was buried in the wings just to get a few more rounds in. I suspect that, in both cases, once they got a solution that worked, the design and test teams moved on to the next thing on the "to do" list.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

I think you've both made good points, but I would point out that neither had fuel tanks in the wings (except the later Mk.VIII Spitfires, which is irrelevant to the discussion, but has to be cleared out of the way!) Both the Hurricane and Spitfire wings were stressed skin, with most of the loads carried by the spars and ribs: I don't see that it would be any easier to add strengthening structure in one or the other. The truss structure of the Hurricane only extended out to the undercarriage. I suspect the Hurricane required less redesign to take the cannon, because of the large weapon bay for four guns rather than two, but this alone can have little effect on the quantity choice of ammunition.

One question I have - did the (as originally desired) 4-cannon version of the Spitfire c wing retain the 125 rounds per gun, or was it then restricted to some 60 per? In which case the two types have much the same, and the answer is that 60 rounds is what the appropriate experts thought necessary.

The point about weight is well made: for both fighters, the 4-cannon version was considered restricting on performance and handling, and saw one pair removed. This was normal on the Spitfire, if less so on the Hurricane.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Here is a link to the Flight magazine on-line cutaways. A great time waster!

http://www.flightglobal.com/staticpages/cutaways.html

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

I have one cutaway of c model and it show drum with cannon. When airplane have drum you could note bulge on the top of the wing (I talk about the Spitfire and Hurricane).

Cheers :)

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

My apologies: I was thinking of the tank before the pilot as the only Hurricane tank.

The Hispano was a heavy gun: Perhaps the Hurricane Mk.IIc manual quotes the masses of guns (or the Spitfire equivalent). I'll dig them out later. Laddie Lucas on Malta was critical of the 4-cannon Spitfire Mk.V, and guns were removed from the Takali-based fighters (not always the outer ones). The Admiralty agreed that although they had required 4 cannon on the Seafire (to take care of BV shadowers on the Actic convoys), the handling and performance were too limited and the service aircraft was restricted to two.

There is a classic historial argument against placing any guns in the wings of fighters, on the grounds of the moments of inertia restricting the agility. Yakovlev (and apparently Lavochkin, judging from his designs) were entirely opposed, although the lighter and smaller Russian cannon would have been less restrictive than the long heavy Hispano. Messerschmitt also disapproved, and the loss in agility from the gondolas on the Gustav are, I think, well recorded in Luftwaffe memoirs. The Fw 190 suffered less, but it did have superb ailerons. Even so some examples were seen without the outer guns, and not just the fighter-bombers.

Today I was looking at the Haynes manual for the Hurricane: it has a lot of interesting items, and some previously unpublished photos. However, from memory, it also has a cutaway for the Mk.IIc. I saw it in WHSmiths at Deepdale, Preston, so presumably it is quite common elsewhere.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Do you mean you have a cutaway of a Hurricane Mk IIC on your website, or do you mean at your home? I looked around your aviation website, but I didn't see anything like that (although there's a lot of other great stuff). I liked the parts about the Serbian air-forces...I've always had a lot of respect for the Serbs fighting qualities.
Anyway, very interesting stuff on that site...I bookmarked it, because I haven't got to check it all out yet.

Cheers!=)

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Yes, just like that. About cutaway- I have it at home, stored. Thank you for the comments about our web site, there is plans to place there from 8000 to 15000 of archive images with various text... long time project.

Cheers :)

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Yes, the same Haynes company - or at least brand name. They did the Spitfire perhaps two years ago, and followed it (I believe?) with the Bf 109. They have now released the Hurricane.

I would not say that "many" Fw 190 pilots removed the outer cannon. Indeed, there was one rather intense debate on LEMB where one poster quite vehemently denied that any such thing had been done, and that no Luftwaffe combat unit would ever have been permitted to do such a thing. Far too advanced an aerodynamic matter for the poor squaddies, apparently. I did point out that such was quite common in the RAF, and that the Luftwaffe's engineering officers were at least as competent as the RAF's, but it made little impact.

I am not going to get further drawn into the wing/fuselage armament, other than to point out that the RN's Seafires were specifically required to carry the 4-cannon for intercepting shadowers, so the reduction to two was clearly driven by more than the advantage in dogfighting. The RAF required 4 cannon for all its fighter desings (initially looking to six on the Meteor and Spitfire Mk.IV) but accepted the limitation to 2 on the Spitfire until the completely revised wing (and more power) of the Mk.20-series.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Perhaps removing the two cannons from the Seafire was in the interests of saving a bit of weight and making carrier-operations a bit easier? I know the Spitfire was far, far from an ideal carrier plane. Reducing the outboard weight a bit might help lessen some of the difficulties of landing on such a narrow-track landing gear? And takeoff, of course, although compared to landing on a carrier, taking off is a piece of cake. I suppose the landing gear made everything more difficult.
It also could be to improve climb rate. I don't know that the Seafire was lacking much in that department, but depending on the height a shadower was loitering at, he might have time to escape before the fighters could reach him. And the lighter armament would also improve range a bit, another area that the Seafire was lacking in.
I don't know, those are all guesses. Have you ever heard a specific reason?
I'm also curious as to what you mean by "accepted the limitation to 2 (cannon) on the Spitfire". Any Spitfire that was fitted with a Universal wing could carry four cannons, if they were fitted. I know that most had Hispano/Browning mixes, but they COULD hold four cannons. I've heard different reasons for this. The original argument for retaining the MG's along with the cannon was that the cannon couldn't sustain fire very long, but once they ditched the drum-feed and doubled the ammo capacity, that wasn't such an issue.
I've also heard things about RAF pilots (at least initially) dis-trusting the cannons, mostly due to the reliability issues that they had during the first attempts at fitting cannon into the wings. I think that those issues weren't entirely cleared up for a while, and the pilots were just getting used to the idea of a all-cannon fighter. And the heavy cannons tended to soak up power and performance, which was a bit lacking anyway. I suppose it makes sense that they'd give the Hurricane the 4-cannon armament first, since after the BoB was over it became essentially a ground-attack plane, and it didn't have to scrap it out in any dogfights.

As for the Fw 190 and it's guns...I've seen a number of photos of Fw 190's lacking their outer cannons, and I've read at least one anecdotal account of an Eastern Front pilot ditching the outer guns to keep up with Soviet fighters. But you're right, and probably most of the Fw 190 without outer cannons were done by the factory or official maintenance units. They were deleted from a number of "U-kit" versions, and from Jabo's. And I don't think the F or G had them either, but that was probably intended from day one, to counter the weight of all the extra armor. And the Dora only had the wing-root guns too, I think.
So, yeah, I probably mis-stated that one. Although who knows...things were pretty chaotic towards the end of the war, and Allied fighters were getting pretty dominant...it seems likely to me that at least a few units did some modifying of their own, but I won't even insinuate that I can prove it!

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

By "accepting the limitation to 2 cannon" I meant that despite a long-standing requirement for a Fighter Command standard of 4 cannon, the Spitfire continued to be acceptable and developed further with only two. Although the C wing could carry 4 cannon, after the initial production it almost invariably did not. There was one SAAF squadron that fitted 4 for ground attack work, and a solitary(?) example of a Mk.VIII in Australia.

The Hurricane got the 4-cannon because the RAF were looking for a 4-cannon fighter (knowing the Whirlwind was not going to be available in significant numbers) and Sidney Camm got in quickly. After the BoB it was clear that the Hurricane was going to be mainly a bomber destroyer (in terms of UK air defence, and the expected BoB Pt.2 in 1941) so the 4 cannon made sense.

I stand by the comment that it was handling deficiencies and performance (in the widest sense of the word) problems that ruled out 4 cannon on the earlier Spitfires. I believe (as opposed to having seen it discussed professionally) that this would nowadays be recognised as a mild form of inertia coupling, but that was not known about let alone understood at the time - it took the analysis of He162 and F-100 crashes to extend the theory.

The Fw190 fighter bombers certainly did not have the outer guns, nor did the inline-engined versions. The LEMB discussion, from memory, was over one of Priller's aircraft, but perhaps you'd do better to go find it and read what was actually said, not rely upon my possibly-distorted memory. I'm not so sure about such things being done in the final days - more likely to just take and use what you could get, rather than waste time messing about.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

A very interesting thread. Just one small observation: inertial coupling is a gyroscopic effect that impacts handling and control, not performance. It is most frequent in aircraft with very low roll inertia (like early small wing jet fighters), and shows up as unintended (and in the worst case uncontrollable) pitch and yaw in response to roll control inputs. Adding heavier guns in the wings would actually reduce this effect.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Yeah, that sounds right. As far as I knew, inertia coupling is an effect of very high speeds and small wingspan. I don't think the Spitfire ever suffered anything quite that extreme...it was laterally unstable and hard to fly in a straight line, but inertia coupling is a potentially deadly effect. I'd think something more like "Dutch roll" would be the case. If it ever got fast enough to be susceptible to inertia coupling, it would have been in a very fast dive, not level flight.
So I can't say which is correct, and I'm curious to find out.
As for the cannons helping stability...I'm dubious. Maybe by adding a little inertia to dampen things a bit, but inertia has it's opposite, momentum.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

I only meant that they would help reduce any inertia coupling.

Dutch roll is present in all flying machines to some extent, and results from the fact that control surfaces will always produce some slight effect in all three axes, even if intended for primarily one axis. It can happen at very low speeds. I've seen it occur in helicopters at 100 knots. Mass distribution will have very little effect on this. Span wise mass distribution can effect roll rate, and has a very pronounced effect on the rate of change of roll rate in response to a control input. Cannon in the wings may slightly increase the maximum roll rate (P), but will have a much more noticeable effect of decreasing the rate of increase of roll rate (P dot) after a given control input. This could be very upsetting to a pilot in air-to-air combat.

All very hard to put in words. A graph would be much easier :D.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Okay, I think I mostly follow you here..."mass distribution", i.e. how far apart the weight is along the wingspan. The more weight you have out in the wings, it will effect roll rate...we had this discussion on a different site regarding the P-38. The way I read it was that the P-38 was a quick enough roller, but it's RESPONSE to the control input was slow...with those heavy engines out on the wings, it took a moment for it to "accelerate" into it's full roll rate. Like a heavy car can have the same top speed as a lighter car, but for the same power, the lighter one will be far quicker "off the line".
Cannon would have a similar effect...between a .303 and a 20mm-armed Hurricane: the wingspan is the same, the ailerons are the same, so the force the ailerons produce is the same, only it's trying to move a much heavier cannon. Friction isn't an issue, so the only effect is that it builds up roll-speed slower.
But part of what I was saying is if a pilot has to use slight OPPOSITE deflection to STOP the roll (the momentum will try to keep the roll going), it will be all the more sluggish on STOPPING the roll. Like the lighter car can out-accelerate the heavy car, it can also stop quicker too. Momentum and inertia involve exactly equal forces...there IS no difference, in terms of physics. An object in space doesn't "know" it's moving; in fact, I think it's aeronautical-engineering lingo to call momentum "reverse acceleration".
But I don't see how cannons could INCREASE the maximum roll rate. The maximum rate would be the same, it would just take longer to build up to that rate (and longer to stop). If heavy cannons increased any performance parameter, it'd be dive-rate! A little extra weight to increase the terminal velocity...although I'm not sure whether in that situation more weight would make a lot of difference, or if it's more about the power of the engine.
I'm curious about that now, too! If a plane can dive at 500mph at full power, how much slower would it be in a glide? The Thunderbolts impressive diving ability makes me suspect that the weight of the plane is important, and I'm not even sure if a prop on full power at 500mph is helping to propell the plane, or if it's just contributing to drag at that point!
Anyway, I guess we can chalk "roll-response rate" up as one potential advantage of a fuselage-gunned fighter over a wing-gunned fighter. All other things being equal (using the same plane, etc.), a Bf 109G with wing guns fitted would be slower into a roll than a Bf 109G withOUT wing guns. Of course, we (mostly) all have heard of how the Bf 109 "Kanoneboote" was disadvantaged by it's wing guns, so now we know why. Although, of course the projecting underwing gondolas would create a little drag, too.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Correct.
Exactly. "P dot" is defined as the rate of change of roll rate with time. Think of the units: degrees per second per second

Yup.

Today an airplane designer calls all this "agility", or the ability to point where you want, when you want, both accurately and quickly. It is a combination of speed of control response (both control input coming on and coming off), sustained rates (pitch, yaw and roll), and repeatability.

The increased inertia can over power the ability to stop or even reduce the rate of roll. Some high speed aircraft have very strict restrictions on roll rate with wing stores, as the pilot soon looses the ability to stop the increasing roll rate, until things start breaking and falling off. Usually this is not desirable.

Terminal velocity occurs when accelerating down forces (gravity plus thrust) equals drag. Extra weight, anywhere, can increase terminal velocity. However, for most modern combat aircraft, and even for some slippery WW2 fighters, this classic definition of terminal velocity doesn't really mean anything. Drag is so low that very high speeds are needed to get drag up to equalling weight. Some other limit will be reached first: structural, aeroelasticity, etc. Today most fighters would start to melt, or just run out of altitude, long before terminal velocity is reached.

Propeller efficiency, and therefore thrust, does decrease as forward speed increases, but I suspect that a constant speed prop would break off long before it even produced zero net thrust. You can produce braking by operating at non-ideal blade angles - reverse thrust as often used on short landings by C-130s and others.

And anyway, speed is not primarily a function of engine throttle setting, but more a function of wing angle of attack. Throttle setting will mostly determine if you are climbing, level or descending at a given speed. The speed, within normal operating limits, is determined by elevator control position and pitch trim setting (if the airplane has this). That is why flying an airplane has been described as rubbing your stomach and patting your head at the same time.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

So what is the definition of "P dot"? I mean, what does it stand for? I can never remember all the jargon, but it's like "Vmax" is the maximum safe speed for whatever operating conditions apply..."Vmax = Velocity Max".
So is the "dot" supposed to be like a decimal or period? Or is it "d-o-t", and the letters stand for something?

And what I was saying about the cannons effect on "P dot"...your first post said:

"Cannon in the wings may slightly increase the maximum roll rate (P)"

...did you really mean to type "decrease"? Because in the next post, you say:

"The increased inertia can over power the ability to stop or even reduce the rate of roll. Some high speed aircraft have very strict restrictions on roll rate with wing stores, as the pilot soon looses the ability to stop the increasing roll rate, until things start breaking and falling off. Usually this is not desirable."

The second makes more sense to me...I just don't see heavy cannons actually INCREASING rate of roll...they'd just make it a lot harder to STOP the roll, wouldn't they? It's funny how even a little weight in the wrong spot can alter an aircraft's handling so much!
What you said about "speed is not primarily a function of engine throttle setting"...that's less true with a powerful combat plane than with a small, docile plane, isn't it? With old biplanes, you climbed by increasing the throttle, and descended by lowering it. But with a warbird, anything over cruising speed is only maintained by high power levels...the second you "let off the gas" it begins to slow down until the drag matches the lower power setting. You CAN maintain speed, by only by loosing altitude. So I can't say that what you said is WRONG, because it's not...but the throttle did have other uses, or at least it was bit more complex than flying a Stearman!
I remember reading somewhere that a pilot could use the throttle to slow himself down and avoid overshooting...the prop acts as an airbrake, and early jet-fighter pilots had trouble adapting to the fact that they couldn't slow down and keep the sights on a target at the same time. You could nose up and slow down, but you wouldn't be able to shoot at the same time.
Of course, that was quite a while ago that I read that...it may be that the guy was referring to the fact that a Me 262 pilot couldn't "chop" his throttles, or he'd flame out the engines. In a prop fighter, even cutting the power while at high speeds will make you slow down quickly, but an Me 262 couldn't do that, and without an airbrake, he was stuck at the speed and power of the engine.
Interesting stuff; it makes me think! Thanks.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

P is rate of roll. Say degrees per second. Anything "dot" to an engineer is rate of change with time. So, P dot (usually written as the letter P with a dot over it, but I can't figure out how to do that here) is degrees per second, per second. If you start with a roll rate of zero, and one second later your roll rate is 90 degrees per second, your average P dot over that one second was 90 degrees per second, per second.

In most aircraft, a roll input (aileron deflection) induces mostly a P dot. I'm using a lot of weasel words here, like "mostly", because I'm over simplifiying. Partly because it's hard to put equations in words, and partly because I've forgotten a lot of stuff. So, with cannon in the wings, P dot initially may be slow to build (because of roll inertia) but it will build. It then becomes hard to stop, again because of inertia. Moving the stick the other way introduces a P dot of a different sign (roll rate starts to decrease, but is still positive for some time). It takes you longer to reduce and then reverse P dot, so P continues to build. That's why you see modern aircraft with restrictions on roll inputs with wing stores or tip tanks. It will get away from you. You will reach a dangerous value of P even after you have reversed the stick.

The short term response to a throttle increase may include a speed increase, but the long term response will always be an increase in climb rate. Modern aircraft have to be designed to minimize the short term response. It's built into the regs a designer has to meet today, but this has not always been the case. But the long term response is built into the laws of physics. Different aircraft may have different short term responses, but the long term response will ALWAYS be the same. This is all complicated when the power change changes the aircraft trim state (due to thrust vector not being aligned with the drag vector). This will be more noticeable in a higher powered aircraft. Then, a throttle input is also partly a longitudinal trim input, and longitudinal trim "mostly" controls speed. But still, the throttle "mostly" controls rate of climb. Notice the weasel word again? What this means is that it is not a case of the pilot "can maintain speed by loosing altitude". The aircraft WILL maintain speed by loosing altitude, unless the pilot does something in the pitch plane.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

To fulfill an earlier promise:
The removable weight of the eight Brownings and 2,876 rounds is 405 lbs.
The removable weight of four Hispanos and 362 rounds is 754 lbs.

So the effect of the cannon would be almost twice that of the machine gun fit.

The positioning of the weapons in the wings would indeed affect handling rather than performance, but the extra weight would affect the climb and acceleration, although not the top speed. It is 2/3 the weight of carrying a pair of 250lb bombs, where the effect on handling etc. is perhaps more easily recognised.

Inertia roll coupling can occur when large masses are offset from the aircraft centreline. The extreme case is of course something like the He162, where the offset is asymmetric. In the Spitfire/Hurricane's case the masses are symmetric; but any yaw and roll, as might well appear in combat, would introduce asymmetries. I'm not strong on stability and control (never was, I was a performance man) but I suspect you are right that the effect would show as a Dutch Roll. Not welcome when a stable firing platform is required.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Forgive me if it has been covered before, lot of text to read, but has anyone thought of the fact that there may not have been a reliable belt fed system at the time of the Mk.IIc development?

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Perhaps, Ruy, but the MGFF seemed to be reliable and the British certainly had examples to review.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

-Ruy-
Well, I don't know if it was entirely reliable yet, but I've discovered that the Hurricane Mk IIC does indeed have belt-feed magazines...as I was beginning this thread, I happened across a photo of RAF armorers loading ammo into a Hurricane MkIIC. It plainly showed the crewman holding a belt of 20mm ammo, and the magazine covers were lying on the wing in beside the openings...it appears that the electric feed-mechanisms were actually fixed to the inside face of the detachable magazine covers. Maybe it just looks that way; here's a link to the page, if you want to see for yourself (the photo is half-way down the page, on the right-hand side.) http://www.quarry.nildram.co.uk/RAF%20guns.htm
These pages are really quite informative..."right up my alley", as they say. I am into guns and weaponry almost as much as war-planes! Maybe you've heard of "Anthony G. Williams"? He made this whole site about aircraft weaponry, etc, and I believe he's an author as well.
Anyway, this is all guesswork, but it is possible that the Mk IIC was initially drum-fed, but switched to belt feed later on in the production run. Somehow I doubt it, but it could have been the case; aircraft have been modified quite significantly, yet still retained the same designation. If a P-47D can either be "razorback" or bubble-canopied yet still be a "P-47D", then I suppose a Hurricane could be a Mk IIC even if they altered the armament a bit.

-John Beaman-
What is your meaning? As far as I know, other than a few minor experiments the MG FF was never belt-fed. Are you talking about the MG 151/20 perhaps? The MG FF had several weak-points, and one of them was the fact that it was restricted to drum magazines that only held 60 (sometimes 90) rounds and were hard to fit into the wing of a plane (same with the early HS.404).
The Bf 109 Emil had a pair of MG FF's in the wings, but the F and G both had single MG 151/20's firing through the engine block. The Japanese used a license-made version, the Type 99-1 and a version with increased power called the Type 99-2. Both were drum-fed.
In any case, having an example of a reliable German belt-feed mechanism would have possibly helped a bit, but not all that much. The problems with making a belt-feed for the Hispano were entirely different than the MG 151. The 151 was designed from day one to be belt fed; the Hispano was designed to have the rounds forced into the chamber from a drum, so there was no ammo-feed pawl to pull the rounds into the gun. That's why the British ended up using the "Chatterault"(sp?) mechanism, an electric motor to pull the ammo-belt into the gun. Basically, the gun couldn't "tell the difference" between that and a drum...the motor simulated the spring-loaded forced-feed of the drum, and so they didn't have to make (very) extensive modifications to the breech, etc to get a belt-fed gun.
In any case, I think most of the problems with the Hispano's reliability came from it's bolt and the fact it was intended to be mounted in an engine-cannon configuration, not on it's side in the wing. I'm sure they had a few wrinkles to iron out with the electric mechanisms, but nothing too serious. It was getting the gun itself to work that was the REAL issue, regardless of whether it was eating ammo from a drum or a belt.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

Forgive me, I mis-interpreted the question.

Re: Hurricane Mk IIC cannon:drum-magazine or belt-fed?
 

That's odd...your post is missing the last sentence for some reason. The notification I received from my Yahoo mail account has a second sentence, about the MG 151. Did the forum screw up somehow? Or was it edited, maybe? It wasn't anything that anyone should take offense over.
Anyway, the MG 151 was a whole different deal...it was designed as a belt-fed weapon, while the Hispano was not. So having access to it's mechanism wouldn't have helped the Hispano at all, unless there was a major redesign of the whole action of the gun. They could have used it to help design a new gun, but I consider the Hispano a superior weapon to the MG 151 in most aspects anyway. I guess a smaller, lighter (and weaker) gun like the MG 151 would have been handy as defensive armament on bombers, etc, or as a vehicle weapon, but there just wasn't time for all that.