"20mm aircraft cannon vs T34/55" Topic

Was watching the anime "Area 88" the other day.

A F-8 strafed a column of tanks (T34 or T55 from what I could see) taking out a few…

I was VERY dubious that a 20mm aircraft cannon could bust a T34/55 (maybe damage tracks etc)…

…or could it? How much armour could a modern 20mm penetrate?

I'd argue that the 20mm cannon would tear the T-34 apart. During WWII Hispano 20mm cannon armed craft like the Typhoon made a mess of Panthers which were the equivalent of the T-34 if not better amred. You also have to remember that the WW2 era tanks were not designed to be top protected at all. Top attack atgw's just simply did not exist.

The Thunderbolt with its 8 .50cals also did abmirable service in its work and actually had a higher throw weight than the Hispano armed craft. THis leads me to believe that the .50 cal armed aircraft are going to knock out tanks as well in a strafing run.

Yeah a high Velocity 20mm Cannon hitting the top deck armor will go right through and probably out the bottom.

The engine deck will be very vulnerable, as will the treads and those spare fuel tanks they always seem to be carrying.

I was dubious about this, but if the Colt Mk12 had an AP round, then a bit of calculation shows that it ought to be able to make an impression on a T-34.

Taking the shot mass to be 210g, using Dehn's penetration formula we would expect the following penetration of 800 MPa steel plate at normal impact:

 200 m/s:   5 mm
 300 m/s:  12 mm
 400 m/s:  20 mm
 500 m/s:  29 mm
 600 m/s:  39 mm
 700 m/s:  50 mm
 800 m/s:  61 mm
 900 m/s:  72 mm
1000 m/s:  83 mm

The muzzle velocity of the Mk12 is 1010 m/s, but there is obviously plenty of scope for reductions due to lowered velocity and angle of strike before the figure drops below the T-34's roof thickness of 20mm, and I should think it could worry the side and rear armour given the probably more favourable angle of strike.

Behind-armour effects, and actually getting hits in the first place, are another matter. And I am not aware of an AP round for the Mk12 -- does anyone know better?

All the best,

John.

…and are they telling?

All the best,

John.

Yes, they have an APDS round in 20mm for American aircraft guns – here is a link to the various 20mm ammunition types. So, I'd say that the T-34 would be horribly vulnerable to the 20mm cannon given their light deck armor.

link

Whoops, stupid me. 100g too heavy on the projectile weight, thanks to brainfart/finger-trouble. That table should be:

 200 m/s:   3 mm
 300 m/s:   6 mm
 400 m/s:  10 mm
 500 m/s:  15 mm
 600 m/s:  21 mm
 700 m/s:  26 mm
 800 m/s:  32 mm
 900 m/s:  38 mm
1000 m/s:  43 mm

…still scope for worrying 20mm of plate, but nothing like as good as a round twice the weight would do.

@Jovian1: The link you sent is the source I used, since I seem to have temporarily mislaid my copy of Tony Williams' excellent "Rapid Fire". You will notice that it lists only an HE round for the Colt Mk 12.

So, the question of whether an AP round existed remains open, as far as I'm concerned -- and then there's the supplementary question of why you would load it for a typical mission.

All the best,

John.

Well, if you're knowingly loading for air-to-mud, I'd request a 1/1 mix of HE and AP, with about every 5th shot a tracer.

If I was loading for pure air-to-air, I'd say 4/1/3/1/1 HE/Tracer/HE/AP/Tracer.

Loading for general patrol, with either air-to-ground or AA, I'd load 3/1/1 HE/AP/Tracer.

John, don't forget that aircraft guns get some free 'muzzle velocity' from the forward flight of the aircraft, but it's 'only' 150-200 m/s.

Well I did consider that top armour/engine decking is pretty weak and a mobility kill seems possible.

However I do recall reading somewhere M48s (comparable to T55) were strafed with 20mm and basically shrugged it off easily (I have no concrete links/info to back this up)

Generalstoner, I have read the ".50 cals vs Tigers" and ".50 cals bounce up off dirt road and kill Tiger tanks" claims with a great deal of skepticism.

Russians had .50 cal specialist anti tank rifles which even when fired point blank in city fighting were only good for knocking out tracks etc.

Hi

the american M2 killed a number of german tanks by bouncing rounds under the tank off the hard pan and through the belly of the tank.

this was post kill analysis I have seen the originals on this.

Rocky

I would also agree that they could have scored a kill through the weaker top armor. Also if F-8's, sexiest jet ever built by the US, were USMC they habitualy loaded a higher ratio of AP.

There are recorded incedents of .50's taking out tanks by bouncing rounds of a road surface but I don't think I've ever seen any of the Big Pussies mentioned, mostly Mrk IV's and below.

Fatman

When figuring out the muzzle velosity don't forget to add in the speed of the aircraft. Even a speed of only 200mph would add nearly 300fps.

Ian Gooderson's truly excellent book "Air Power at the Battlefront" shows that very very few German tanks were ever knocked out by Typhoons and Thunderbolts, whether with 3" RPs or strafing – but that:

a) they had a huge effect on the B Echelon softskins (eg tankers) without which the panzers were quickly useless; and

b) the average tank crewmen only had to see the results of one 3" RP hitting a panzer (even with a PK of 0.5% or thereabouts) to think twice about staying in his tank when the Tiffies were about.

His conclusion (based on the wartime operational research) is that the tactical fighters had a massive impact, just not quite in the way the pilots thought they were with large numbers of panzers blatted directly.

Hi

Historically, everyone over estimates their effectiveness. Smoothbore muskets to modern.

As gamers, however, we like to think more dramatically.

As with many threads, you often win by just putting rounds on target and having people put their heads down or even retreat for cover.

Rocky