.303 vs 20mm

[Airspeed]

Thank you Peter
Evidently some image distortion when I resized the projectile to 20mm.
I can hear it coming now....you're going to tell me that the gun barrel is a nominal 20mm, but the projectile is slightly smaller because that copper ring takes up the slack?

[petermcleland]

Thank you Peter
Evidently some image distortion when I resized the projectile to 20mm.
I can hear it coming now....you're going to tell me that the gun barrel is a nominal 20mm, but the projectile is slightly smaller because that copper ring takes up the slack?

That is exactly right Mike...The projectile sides barely touch the lands of the barrel rifling, but the copper ring is deeply cut into by them.

[Chris Trott]

Mike, while your round may not be correct for a WWII 20mm round, its dimensions and profile look to match those of the M53 Armor Piercing rounds or M55 Training Rounds used in modern 20mm cannon. You can see pictures and info here - http://www.aircav.com/cobra/ammo20.html

[Airspeed]

Again, thank you Gents.

Peter, I've seen rifling grooves in a fired round photograph, and they certainly are deep, but nothing to show on the lead bullet.

Chris, you're right, that does look a lot like the one I bought. Vietnam vintage. At least now I can label it as such!
The whole shebang was a big outlay for me, so it'll be a while until I look at doing any 1940s ammo.

[petermcleland]

Again, thank you Gents.

Peter, I've seen rifling grooves in a fired round photograph, and they certainly are deep, but nothing to show on the lead bullet.

Mike, the bullet or projectile is made of steel...That's why they don't want it to scrape the barrel rifling. On the proper ammo it is hollow and filled with explosive...It is very interesting to fire a long burst of HE at a target on the ground (I once did it to a spitfire on Salisbury plain)..There is a rapidly approaching firework display in front of you with an absolute hail of debris and stuff being hurled back at you by the ammo exploding. On that same attack on the spitfires a friend in the formation was a bit late breaking and collected a fragment of debris through the bulge in his canopy...It missed his head and lodged back behind him in the ejection seat. We discovered that it was a steel disc with a copper band on it (the complete base of a 20mm HE round)...It is a sobering thought that every round of HE that you fire at a ground target will explode and fling back this copper banded steel disc roughly in your direction

[Airspeed]

Well, there you go!
I knew of ordinary, HE, tracer, and incendiary, but didn't realise that they were encased in steel back then.
Were the .303s lead?
I've not been a student of war, my interest is all based on the visual attraction of aircraft of that era, when prop. aircraft design was pushed to the limit by the pressure of war.
I really do learn something every day.
Glad that your companion dodged that bit of steel.

[petermcleland]

The 303s were copper jacketed lead and the jacket encased the whole bullet. The rifling engaged most of the length of the bullet.

That attack was actually three firing runs with two sections of four Venoms...The first run we all fired a salvo of four HE headed rocket projectiles (RP) at two Tanks...The second and third run were 20mm cannon attacks with the ammo belted 2 and 2 (High Explosive Incendiary and Semi-Armour Piercing Incendiary...HEI and SAPI). The targets for these two runs were 6 Spitfires, 1 Meteor VII and 12 3-ton trucks, all filed with petrol and old tyres.

I flew number 2 to the Boss...number 8 forgot to set a switch to RP for the first attack and went rather low while repeatedly pressing the fire button...His rockets did not go and his Venom was damaged as he got too close to other peoples explosions. We had to leave his Venom behind for repair when we flew back to our base in Germany.

I destroyed one Spitfire and shared the Meteor VII...Due to the low cloud base we were not able to get a real 30 degree dive angle for the rocket firing so I think the two tanks survived but all the aircraft and vehicle targets were left broken and in flames...It was all great fun and an experience I never forgot. It was on 2nd July 1954 and I was 21 years old...Great Days!

This took a bit of finding but it is the Target photograph:-



Click it to enlarge it, then the Meteor is easy to spot and my Spitfire is the darker one to the Meteor's 11 o'clock the Trucks are near the bottom of the picture and the Tanks are up near the top.

[DaveB]

A nice link to Wiki ref FMJ bullets Mike (though I'm sure you've already seen it).. https://en.wikipedia.org/wiki/Full_metal_jacket_bullet

ATB
DaveB

[Airspeed]

A nice link to Wiki ref FMJ bullets Mike (though I'm sure you've already seen it).. https://en.wikipedia.org/wiki/Full_metal_jacket_bullet

ATB
DaveB

Thanks Dave; added to my sagging memory

Interesting pic, Peter, thanks for digging it out.