Was .303 the smallest calibre mg used in WW2 aircraft? (1 Viewer)

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... he basically says words to the effect of: "we could have had it all very differently but basically the Air Ministry and the turret people just sort of didnt really bother themselves".

This isnt true.

I'm no expert on the subject but the existence of the Rose turret seems to validate Harris' summarized version of events.
  1. Years of unsatisfactory progress on turret development
  2. In exasperation BC skips over Air Ministry / MAP and asks Rose Bros. to develop a turret
  3. Rose produces a turret arguably better than the FN or BP turrets -- and in service before the other firm's turrets
 
Brits didn't have 50 cal turrets or cannon turrets for a combination of reasons. I think what Harris said quoted above is basically nonsense. (As In I'm sure he did say that but it doesn't tally with the air ministry files). There was a big supply issue early on with 50s and the cannon turrets were so heavy it necessitated reducing the bomb load to the level where it was calculated that you'd need to fly more planes over the target and you'd end up with the same aircrew losses anyway. I'm not 100 percent sure I agree with all the reasoning but that was how it was discussed at the time.
Harris seems unaware of the extreme difficulty of building a workable 20mm top turret. The gun barrels of the Hispano-Suizas are very long and exert a tremendous force when traversed toward the side. Remember, you get lever arm effects, which are oh so fun for the engineers to work with.

You got two effects. First, the turret hydraulics got overloaded by the force exerted on them, so they could barely traverse forward, they traversed aft too fast, and the rate of traverse was irregular, making tracking targets nearly impossible. Second, the drag on one side was sufficient to to yaw the aircraft a bit, and the yaw would change as the turret traversed, which made aiming still harder and was disconcerting to the pilots and the rest of the crew. It's always great for navigation when the aircraft is yawing back and forth just enough to matter.

You could build in a counter-drag system the way that the Italians (and Soviets) did, but you end up with a ridiculous airbrake when the guns are traversed directly to the side.

The other problem was the sheer size and weight of the turrets. You simply couldn't build a realistic 20mm turret at anything like the diameter of a .30 turret. 20mm Hispano-Suizas are also tremendously heavy, the ammunition is very heavy, and they require electric drives to pull the ammo in. Oh, and you can't use the standard electric motors from fighters because you won't be pulling the belts horizontally through the wing, you'll be pulling a loaded belt up, possibly from below the level of the gunner's feet.

The B-36 solved these problems by being frickin' huge.
 
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What's the largest non-cannon machine gun round used in ww2 aircraft? Some sort of 30mm solid shot?
We have some confusion as what is a cannon and what is a machine-gun. Some countries changed the definitions a bit but in general machine guns were under 20mm and cannon were 20mm and up. 15mm guns are a bit iffy.

This is regardless of the type of projectile, a solid shot projectile does not turn a cannon into a machine gun.

A major difference for most people was the construction of the projectile

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Machine guns (small arms) tended to use a jacket material that would upset on firing to fill the groves (or swage down).
Cannon , because of the steel shell bodies, just about always used "driving bands" usually copper unless shortages required soft Iron. The projectile rode on the lands of of the rifling and only driving band engaged the rifling and got engraved.
img26.jpg

Obviously fitting driving bands required a lot of work/machining.

cannon is not a synonym for gun that fires HE ammunition.
 
We have some confusion as what is a cannon and what is a machine-gun. Some countries changed the definitions a bit but in general machine guns were under 20mm and cannon were 20mm and up. 15mm guns are a bit iffy.
This is regardless of the type of projectile, a solid shot projectile does not turn a cannon into a machine gun.

A major difference for most people was the construction of the projectile

View attachment 693130
Machine guns (small arms) tended to use a jacket material that would upset on firing to fill the groves (or swage down).
Cannon , because of the steel shell bodies, just about always used "driving bands" usually copper unless shortages required soft Iron. The projectile rode on the lands of of the rifling and only driving band engaged the rifling and got engraved.
View attachment 693131
Obviously fitting driving bands required a lot of work/machining.

cannon is not a synonym for gun that fires HE ammunition.

One problem with using this as a demarcating for what and what is not an autocannon is that the 13x64B round used in the MG-131 has a driving band, while the much more substantial 14.5x114mm ammunition used in the KPV and friends does not, meaning that the smaller and weaker of the two is the autocannon while the larger and far more powerful of the two is the mere heavy machine gun.
 
One problem with using this as a demarcating for what and what is not an autocannon is that the 13x64B round used in the MG-131 has a driving band, while the much more substantial 14.5x114mm ammunition used in the KPV and friends does not, meaning that the smaller and weaker of the two is the autocannon while the larger and far more powerful of the two is the mere heavy machine gun.


A major difference for most people was the construction of the projectile

Machine guns (small arms) tended to use a jacket material that would upset on firing to fill the groves (or swage down).
Cannon , because of the steel shell bodies, just about always used "driving bands" usually copper unless shortages required soft Iron. The projectile rode on the lands of of the rifling and only driving band engaged the rifling and got engraved.
Yes there are cross overs.
 
that may be (or may not?) because most of the ammo was AP, APT, and a bit of ball.
NO HE and no incendiary rounds.
With no HE is it a cannon?
Or a rapid fire anti-tank rifle or...................................

The 12.7-19mm area is rather grey. It may depend on what the maker or the country buying it wants to call it.
Trying make under 20mm HE was done but the volume of the interior of the projectile goes down with the cube of the caliber.
 
How about simple economics. There were millions of .303 rounds left over from WWI. The light BMG .303 was readily available & in full production in the UK? Also British production of the .303 round was well established & a MG is useless without ammo. Then you add in redesign to accommodate the BMG .50 & its not hard to see a delay in getting them into the aircraft
 
How about simple economics. There were millions of .303 rounds left over from WWI.
Except the left over WW I ammo is NOT what you want to be shooting at aircraft even if you keep the .303 guns.
No left over incendiary ammunition.
No left over armor-piercing ammunition

and having aircraft guns jam because you are using cheap, 15-20 year old ammo is truly false economy. The whole idea of going the Browning was to allow the guns to be mounted out of arms reach of the pilot. Once a gun out reach of the pilot jams it pretty much stays jammed until the plane lands.
 
Yeah my understanding is that newer, nitro-cellulose ammunition was always used by the RAF vs. all the old cordite.
 
Yeah my understanding is that newer, nitro-cellulose ammunition was always used by the RAF vs. all the old cordite.
It is not even the nitro-cellulose, old wartime brass had tendency to split or crack upon firing.
It is one thing to have a few problems (2-3 bad rounds per thousand) in bolt action rifle.
In an eight gun fighter that is carrying 2400 rounds having the same failure rate could jam 50% of the guns or more.

You want the best quality ammo you can get for aircraft guns.
 
Except the left over WW I ammo is NOT what you want to be shooting at aircraft even if you keep the .303 guns.
No left over incendiary ammunition.
No left over armor-piercing ammunition

and having aircraft guns jam because you are using cheap, 15-20 year old ammo is truly false economy. The whole idea of going the Browning was to allow the guns to be mounted out of arms reach of the pilot. Once a gun out reach of the pilot jams it pretty much stays jammed until the plane lands.
Agree, but with high stocks of WWI ammo it was available distribute it to the ground troops. That would free up .303 production facilities to lean heavily in production of aircraft rounds till the entire logistics system caught up. Also the large scale production of the .303 BMG was also in place but not for .50BMG rounds delaying the introduction of the large Browning on aircraft.

First .50 production was 1926 for British military trials, but there was little British official interest after that until WW2. The 1920s/30s Kynoch production was mostly for export.

During WW2 the UK imported large quantities of US ammo and the guns to fire it for Lend Lease aircraft and vehicles. There was also some British production at Spennymoor Royal Ordnance Factory in 1943 and 1944 of ball, tracer and AP plus some experimental types.
 
It is not even the nitro-cellulose, old wartime brass had tendency to split or crack upon firing.
It is one thing to have a few problems (2-3 bad rounds per thousand) in bolt action rifle.
In an eight gun fighter that is carrying 2400 rounds having the same failure rate could jam 50% of the guns or more.

You want the best quality ammo you can get for aircraft guns.
Hi
Yes, you do need the best quality ammo, this was realised during WW1 and the British did endeavour to achieve higher standards, the OH of 'The Ministry of Munitions Volume XI' has the following:
Image_20221121_0006.jpg

There were problems in production indeed the .303 ammunition manufactured in the USA had a poor reputation for quality:
Image_20221121_0007.jpg

Image_20221121_0008.jpg

Mike
 

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