IIRC they were originally MKll A Series 2 , when they first were introduced? They became the IIB shortly after.

For clarity could someone define the difference between 'Cannon' and 'Machine Gun' please?

Thanks.

There isn't a universally accepted definition but we (RAF that is) tend to regard anything above 14.7mm as a cannon but other factors are considered too. Cannon projectiles are typically large enough to accept an HE charge (amongst other options) and usually fired via an electric impulse (rather than striker fired) and typically employ either a rotating breach or barrel (rather than a simple reciprocating mechanism).

For aircraft the 'cannon' term is an abridged form of auto cannon or rotary cannon, but most aircrew just call it a gun.

I was once told that a machine gun could be carried and fired from a standing position by a human being type person, a cannon would need a mount of some sort.

Did you ever put this theory to the test?!

I asked a wartime Spit pilot why you never saw the Mk IX in four cannon fit. They had the fitting for four cannon but only carried two. Apparently the wing flexed so much when firing four cannon that aiming became pretty much useless.

As has been noted, the early F4 carried only four 50 cal guns. There was some opposition from pilots when they released the six gun wing as the ammunition carried for each gun was less, and as the pilots figured, if you can't hit a target with four guns you're not going to hit it with six.

WW2 German aircraft weapon designations seem to have a clear demarcation of machine gun -up to 20mm and, machine kannone for 30mm weapons. Cheers

OAP

I recently read "MIG Menace Over Korea" by Nicolai Sutiagin (22 kills) and he was quite derogatory about the F-86's armament. He said they often found strikes on their Migs where the .5 bullets had bounced off.

The F-86 armament of 6 x .50 cal MG was not effective. The US Navy instead incorporated 4 x 20 mm cannon into it FJ-2 Fury II proving the airframe could accommodate them. Unfortunately they were too late to take part in the Korean War and thus prove the superiority of the 20 mm cannon against the .50 cal mg.

What tends to be forgotten is that the P-51 started life as a British aircraft, albeit designed and produced in the USA. It was built to specifications laid down by the British. No modification was necessary upon arrival in the UK. The P-51 came with all the items you list Harry. Windscreen was 1.5 inch armour glass,the pilots seat had a 5/16 inch plate from just below the seat to a point level with his shoulders and a 7/16 inch plate above this to protect the head, a 3/8 inch thick firewall, armour plate forward of the coolant tank, and self sealing fuel tanks. You can see the British bought their combat experience to the design.

Early versions of the P-51 had four 20mm cannon, a report written on 30 December 1942 recommended changing from the 20mm to .5 inch because,It doesn't spell it out, but infers to me that stoppages were a problem.

Indeed - tho to be pedantic the British ones were NA-73's and NA-83's and because we'd spec'd them they came with most of the necessary kit -and adding the "Merlin" later made it the best fighter of WW2

Somewhat off topic but reading around I never realised that the P-47 bubble canopy was adopted after they tested it with a Typhoon canopy.. I think the P-51 canopy was a US improvement over the UK part bubble canopy adopted from the Spitfire

Stoppages always were a problem with early wing mounted Hispanos and continued to be a problem until the later Martin Baker belt feed mechanism came into use. The Westland Whirlwind which came into service around the time of the Battle of Britain had four nose mounted Hispanos and suffered with far fewer stoppages. This led to the belief that the cause of stoppages in the early Spitfires was due to the wings flexing. This may or may not have been a contributing factor as the later Hurricanes which had a stiffer wing had fewer stoppages than the Spits. However probably the most likely cause was firing while pulling more than about to two "G" which was inevitable with most deflection shooting. This problem remained with the Meteor night fighters right up until they were withdrawn in the early 1960's even though they had MB belt feed mechanisms.

Thank you. I get confused when people use .50 Cal and 30mm etc

In modern parlance, surely a cannon fires explosive-filled rounds while a machine gun fires solid projectiles, including tracer rounds?

IIRC he chose to attack from head on to avoid the 20mm defensive armament - and shoot into the cockpit...

Well, they won so something went right....

the Move to 20mm Hispano and ultimately 4x of such...

No - that's not the definition of cannon. Its about the caliber.

I'm going to step out on a limb here and probably get flamed, but when you say "stoppage" I infer that to mean that the weapon was prone to jamming, and that the term has nothing to do with its actual effectiveness in "stopping" an enemy aircraft. Is that correct?

Sorry, but British is not my first language. :O

That is correct. Never be afraid to ask. :)

. The problem with the early cannon Spitfires was that the cannons were laid on their sides (rather than their belly) and were drum rather than belt fed. The reason they were laid on their sides was due to the shape of the Spitfire wing. Stoppages were an early problem. These issues weren't ironed out until autumn 1940. The early 8 gun, then 4 machine gun /2 cannon and later 4-8 machine gun and 2-4 cannon Spitfires, all had different wings.