After rechecking... 4x303 would only have weighed around 100-120lbs while 2x HS 20mm weighed about 190-210lbs . This a fairly substantial difference, and would reduce performance somewhat for certain. I haven’t calculated comparative ammo weight, but 20mm is a lot heavier than 303, so I’d expect that to reduce performance as well.

It wasn’t’t common, but the C wing could easily handle it, and it did see service. More commonly- particularly in Malta, where conditions were harsh and supplies low, the spit V was often flown with just 2x 20mm.
Finn

There are only 3 photos I could find showing 4 cannon. Lots of talk in other forums about this saying it didn't last long in service use. A few different reasons such as problems with gun heating and weight effecting maneuverability being 2.

One is of a delivery to Malta where they needed cannons to replace the breeches that the limestone dust infiltrated and wore out more quickly. They added them to these carrier launched replacement aircraft and deleted the .303's, since they used only 1 .303 in service at Malta and had plenty of them. When launched they were loaded with only 60 rounds in 2 of the cannon.

One is of a 2nd SAAF aircraft.

The last is of supposedly a wing command gent who kept his 4 cannon.

Basically rare as hen teeth.

Some sources about G-suits;

Gear Up... by Jon A MacGuire, P-51 vs Fw 190... by Martin Bowan, To Fly and Fight by Clarence "Bud" Anderson,

Hellcat by Barret Tillman, Pacific by Hugh Ambrose, Pursue and Destroy by Leonard "Kit" Carson,

Bluenoser Tales editor Robert H "Punchy" Powell, Airwar by Edward Jablonski.

Also of note: "engineering records of the 504th FS on 26 June 1944.

Fencer

So let's do a variant with just 2x20mm. That would be lighter, and would demand accurate shooting. Could be fun.
I don't think the extra 2x20 would affect maneuverabilty too much; the added weight would be equivalent to about 20 gallons of fuel wouldn't it? Go here for a performance report of the SpitVC with 4x20, in which states there is no difference in handling: http://www.spitfireperformance.com/aa873.html). But of course, let's not put
the 4 cannon spit in the game if there were only a few actually in combat. The 2x20 would be fun tho.

All Spitfire V variants already have 2 x 20mm (Drum or belt fed) along with 4 x.303.

I don't see much benefit in having 20mm options without the .303s.

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It is fairly easy to add a loadout option to the existing Spitfire Vc with only 2x 20mm in the menu where you select bombs/drop tank etc. It would however require the implementation and process of adding a whole new 3d flightmodel if we also want to model the greater roll rate and general agility that a real life Spitfire Vc would gain from not having the weight of 4x .303 cals in the wings. I agree with Bollok that it would not be worth all the work. The roll force, roll weight and agility etc of the flightmodel are set in separate parameters in another file, and the different guns loadouts for a specific flightmodel only adds to the total weight of the aircraft, the weight is not calculated to affect the plane from the point where the gun is placed. As such the roll performance won't be improved from deleting the .303 cals.

If wanted though I could easily add the armament option of only having 2x 20 mm cannons to the existing Spitfire Vc. I've tested it and it only took me 5 minutes. The benefit from choosing this armament option is a 200.1 lb lighter plane, which could be a tactical choice if dueling other Spitfire Vc's since the climb rate and sustained turn rate would see a small benefit. The downside is worse firepower and the Vc will not, due to the how the code works, benefit from an increase in roll rate and agility as a real plane would have.

The question is just how common this loadout was in ww2.


<S>
/Robert

The reason the British went to a shorter barelled 20mm hispano Mk V on their tempests was not so much overall weight but reducing the extra weight and a big massive gun sticking way out into the slipstream. When you look at aircraft guns one of the values they compare them by is the quality factor or Q. It is basically a power to weight ratio of the gun and the bullet it delivers. The Hispano Mk V and B20 are excellent guns in this regards. The Hispano Mk II is not too shabby either but significantly less Q than the other two. Year ago, our squadron talked to RCAF ace Rod Smith about typical RAF aircraft armament and he was of the opinion that two hispanos were more than enough, he didnt think he need more than that to take down fighters over Malta or Europe.

http://users.skynet.be/Emmanuel.Gustin/ ... un-pe.html

well, you'd lose about a 100-150 pounds in weight between the 303s and their ammo.
In a light aircraft, that could make a little bit of difference in climb and turn rate.
The 303's aren't much use at all in the Spit anyway. As far as I'm concerned, when you're out of cannon in a spit V, you are out of guns.

finn