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.

Classic example is that massive cannon on the A-10. It's designed to fire solid projectiles at extreme velocity (and extreme rate of fire) with the ability to penetrate heavy armor.
I suppose it would be possible to use an explosive round in the A-10 cannon but if it's ever been tried or even proposed I've not heard of it.

Not quite correct, the A-10's gun also fires a high-explosive round - the PGU-13/b High Explosive Incendiary (HEI) cartridge. The 14/b round is API with a depleted uranium core.

Was the British who developed the techniques necessary to mould a teardrop canopy.

TBH I believe that was the case with the F-51 and the initial P-47 test but that the 'Mericans came up with an easier to build model for the P-47

Interesting - has the HEI ammo ever been used in combat? Serious question (not yanking your chain), I'm curious - because everything you ever see or hear about the A-10 is tank busting with those API rounds.
I recall seeing an interview with an A-10 pilot who got an air-to-air kill when he came across an Iraqi helicopter (I'm thinking the First Gulf War, but I could be wrong). Anyway he said something like 'I gave it a five second burst and there wasn't much left...'.

Think most current usage has been the HEI ammo, API isn't really that well suited against unarmored targets...and not many targets while running air to ground in Afghanistan is armored.

There's an HEI round - PGU-13/B

https://www.prnewswire.com/news-rele...120058399.html

https://www.gd-ots.com/munitions/med...n/30mm-gau-8a/

All those different wings cannot be good for mass production, nor for logistics/maintenance. And that was one big reason why the US pretty much standardized on machine gun armament. It greatly simplified production as well as logistics.

The Dutch ship protection GoalKeeper CIWS system uses the same gun as the A-10's. I should imagine the standard round would be the HEI ammo and it has been used in combat against Somali pirates.

It's not as bad as it sounds, by late '41 early '42 the Spitfire Vc was introduced with the universal wing that could carry any of those combination of weapons. Bear in mind there were other modifications being made to the wing as the aircraft evolved to strengthen it and ease production so it's not as if a wing from a Mk1 would have worked on a Mk9 anyway.

http://spitfiresite.com/2010/04/conc...g-types.html/2

"All those different wings cannot be good for mass production"

true but they were evolving rapidly to meet a whole bunch of different threats - from 1938 - 1943 things moved on a very long way

And yet one of the most scary / educating / informative experiences of my life was as a 16 yr old [err yes, MANY years ago] crossing a 1km wide plain, along with the other 150 lads on that ex .... when 3 x A-10s turned up.

Whichever way we looked or faced there was always one threatening us, and another turning hard to engage. Our 7.62 rounds would probably just have bounced off anyway, had we even managed to hit it (because you were almost too busy looking for No.3 who was [panto time: Behind You!!)

Hmm, that told me a lot about numbers of a/c and how troops on the ground can or do react to one a/c or more than one a/c. And how many directions a person can look in at any one time..

CS

Just found this: about fitting .50 cal Brownings to Spitfires.

An interesting paragraph:

It should be noted that compared with other aircraft weapons of the day, the performance of the Browning was rather undistinguished, especially in comparison with aircraft cannon widely used by other combating nations. The American gun was also very heavy. On the other hand, the USAAF had found it extremely reliable and simply “good enough” in air-to-air combat. This way the Browning became standard armament on American fighters – the P-51 Mustang, P-47 Thunderbolt or the F6F Hellcat, and more, with the same arrangement retained even for F-86 Sabre in post-war years.

Lots of good points raised here, but some interesting exceptions to the standardised 50 cal could be found. The mention of the P39 cannon doesn't convey what must have been a supply nightmare as some squadrons in the early days in New Guinea, equipped with a mixture of P39's & redirected p400's. That resulted in - 30 cal bmg in the wings, 50 cal in the nose, 20mm in the nose (p400) and 37mm in the p39. A logistics nightmare. And how about the modified field gun in the B25 (h?) On teh opposing side, The Zero packed a very interreesting licence-built 20mm Hispano that weighed much less than a 50 cal. I cleaned up one salvaged from a wreck in the sea and was impressed with its small size & light weight, part of the weight saving for the Zero. Low velocity, only 49 (I think ) rpg but very effective in the right hands, vide Saburo Sakai. Finding various often non-standard installations from both sides made for some interesting analyses.

Ted Parks description of the P39/P400 cannon - because it was mounted in the prop shaft - he said...

The P400 was also sometimes humorously referred to as a P39 with a Zero on its tail :)

the above quotes coming from one of Ted Parks books - either 'Nanette' or 'Angels Twenty' - cannot remember which - he flew P39/P400 ops in NG.

Just mentioned for historical accuracy. The Zero used Type 99 Mark 1 cannon and Type 99 Mark 2 cannon which were Japanese versions of the Oerlikon FF and Oerlikon FFL.

Mine came as the subject of 3 circling Apaches having been stopped by protesters near Srebrenik, BiH back in the late 90's.
Young and dumb (and firmly believing our "freedom of movement") I didn't take the hint of a long line of parked up cars and blew right past them just to get stopped a km further down the road by hundreds of peaceful protesters blocking off the road.
3 Swedes (2 logistics and our female chaplain) in one truck. No end of talking could get us trough but just as we were about to do a 59 point turn and head back a US convoy pulled up on our arse. :sad:
Lots more talking and hand waving took place and during that someone must of called it in and the Apaches appeared.

Eventually it took the better part of an hour to get the whole gaggle turned around and ending up with a detour back to Brčko, Čelić, Lopare and Tuzla to finally get us back on base.

Oh the memories!

WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

a great treatise on the mg vs cannon debate

http://spitfiresite.com/2010/04/cann...ntroversy.html

Thanks for the correction, Megan, I didn't have access to references at the time and the drum feed fooled me. Very impressed by the quality of steels and engineering, also the fact that it was, or appeared to be, a simple blow=back design firing from an open breech. On a different topic, and from somewhere earlier in the thread I noticed a quote from someone that an mg "should be able to be carried & fired by one man". I knew an armorer who tried the experiment, in Korea, of firing a .50 cal "from the hip", braced on sandbags, held down with all his weight. Luckily he only put three rounds in the links. First round somewhere near the target, second at 45 deg elevation, third vertically upwards, armorer flat on his back.

Anyone with information as to the nature of the problems the US had in producing the Hispano 20mm. Would have thought mass production to the necessary tolerances would have been a given for the nation.

Edited to add: I think my question will find an answer here somewhere.

http://www.milsurps.com/content.php?...ge-M.-Chinn%29