20 pounder vs. T54's front hull

[Aeraaa]

In the game the 20 pounder's APDS shot has a penetration value of 30. While this is correct for armor sloped at 0 degrees from vertical, it is not the case for its performance vs. sloped armor. The frontal hull of T54/T55 is 20 IIRC, which is it's LOS thickness, but not its actual effective thickness vs. contemporary rounds. The result is that the 20 pounder can kill T54s frontally up to 1800 meters, while in reality it would struggle against the T54's hull armor even at very close ranges.

I think the gun's penetraton values should be corrected, as now it is as effective as the APDS of the L7 gun, the latter of which was made to combat the armor of T55.

[Suhiir]

Unfortunately WinSPMBT doesn't directly deal with armor slope, it's just factored into the armor value a vehicle is given.

Could it be the frontal armor value of the T54/55 is to low?

[Mobhack]

T54 turret front is 23 in game terms. Not 20.

30cm at the muzzle, 29 at 500m, 27 at 1000m, etc as shown in the table for it at this site: http://www.wwiivehicles.com/great-br...ion-tables.asp

Running the APCALC utility, it gives 30 at the muzzle for 20pdr 52 (presumably the Mk. 3 APDS), 27 at 500m, 24 at 100m. So its actually a smidgeon under-performing in the game.

Final range bucket where armour pen equals the front turret of t-54 is 1200m. (If defending armour is equal to the pen value, it is not a guaranteed pass-through). Also, on the game map the firer is not always at a 0 degree angle-off, so the effects of the target angle-off will usually reduce basic penetration somewhat.

The 105mm L7 1959 model APDS will do a T-54 front turret to 1500m using APCALC, again in perfect conditions.

The 20 pdr was a very good gun, but had reached its ballistic limits. The 105mm allowed more penetration at a longer range, but the main thing it really brought to the table was a calibre useful for chemical energy munitions (HEAT and HESH).

20 pounder centurions do about evens against T-54s at 1000m and under in the game, but the T-54 tends to plink a few of them back using the 3-5 HEAT shells they carry by the time the up-armoured models arrive. And they can do tat at long range too, which is annoying. Plus centurions are slow, so will often lose any manoeuvre battle against a thinking opponent. If trying to stop a horde of T-5X with Centurion III with the original armour suite, you will lose quite a few..

The data wont be changed. 20pdr APDS was twice as energetic as the WW2 German 88L71 at the muzzle after all. It was rather a hot gun. It is not a wonder-weapon, though.

[Imp]

I only had a quick look for real life stats Which look about right for the gun, did not look up stats for L7 iwhich in game is only marginaly more effective than the 20 pounder.
At your quoted range of 1800m L7s penetration is only +1 on the 20.

Quick look also T54/55 armor looks right the angles already factored into the game stats. Armour was roughly 100 at 60 degrees which is 20 as represented in game.

So yes I would expect the 20 pounder to kill a T54/55 easily at close range, 1800m the oucome will depend on how lucky your die roll was the result could be kill damage or no effect.

[Imp]

Ha phone call means got pipped, front hull is 19 or 20 in game dependant on model which fits RL

[DRG]

Armourcalc is included with the game........10cm @ 60 degrees = 20 and that's what it gets so YES slope IS factored into the equation for all amour values and 305mm is what a 20 pounder APDS could penetrate and in the game that's what the 20 Pounder 52 is rated at....... the 20 Pounder 50 OTOS only gets 24 and at 1000m the sabot pen for the 50 is under the t-55's armour but the "best pen" ( because we toss a host of possible variables in ) is 23 so in some cases it could.

The numbers we have in the game reflect the correct information available ---including armour slope which is always factored into the armour data

That said this LINK gives this data for the 20 pounder


The problem with some of these reported angles @ is they can be reported two ways....90 is verticle so that is also zero inclination..enter 90 into armourcalc and it gives an impossible number so for this it tell me that with perfectly vertical target armour the APDS will penetrate >200 at 1500m but not penetrate at 2000m and APCalc agrees ...it gives 19 pen at 2000 but MAYBE 23

What I wonder is.....we give the 20 pounder tanks nothing but APDS , none I have found carry APCBC but IDK what ammo loadouts for those tanks were ATM------further EDIT..........http://www.lancers.org.au/site/Centurion_Tank.asp........

Ammunition: 65 rounds comprising; Armour piercing discarding sabot (APDS), High explosive, Canister and Smoke.

so sabot and HE only as we have it

and YES..THIS data ( there will ALWAYS be difference is data like this ) claims best pen for the 20 pounder is 285..rounded up it's would be 29 in the game..... IF this data is accurate.. and that one cm difference translates to about 200 m difference in the game.....you get 1700 results at 1900 re : 29 pen vs 30 for "basic" sabot ( not best sabot )


This link http://www.wwiivehicles.com/great-br...ion-tables.asp

for the 20 pounder APDS MK3 at 500 yards =

11.61"

that's 29.4894 CM

Don

[Aeraaa]

As i said, I know that 20 pounder can penetrate a bit over 300mm of RHA without slope. The problem lies in that its performance drops a lot against sloped armor (especially against highly sloped armor like the T54s front hull), so no, a simple x/cosθ will not give the effective armor thickness of the target. The only rounds that follow the above simple equation relatively close are HEAT rounds, but none of the KE rounds do(modern APFSDS are better in this and some like DU penetrators are actually better against sloped armor than vs thick unsloped one, hence the boxy design of modern MBTs). Anyway, in KE rounds, things like thickness/diameter ratio, armor quality projectile speed etc give very different results that vary from round to round and in the case of APDS rounds a slab of armor of 100mm RHA sloped at 60 degrees from vertical has 3.5 effectiveness against the incoming round, which makes the T54s hull a very hard nut to crack even at point blank range (source: WW2 ballistics armor and gunnery by Lorrin R. Bird and Robert D. Livingston pages 30-31, although it speaks mainly about 17 pounder, 20 pounder wasnt much different).

Btw DRG the link you gave is from warthunder and after many updates this games handles sloped armor differently. 20 pounder now penetrates 80mm @60 from vertical, compared to the 100mm @60 needed to defeat the T54's front hull.

[Aeraaa]

Oh, and here's another link that mentions what I've said: http://www.dtic.mil/dtic/tr/fulltext/u2/a954868.pdf

On page 6 it says: "Since the HEAT shell does follow the cosine law, a round which can penetrate a 12 inch plate at normal obliquity, can defeat a 6 inch plate inclined at 60deg obliquity. For comparison, the 90mm HVAP M304 shot can defeat 12 inch plate at 0deg obliquity, at ranges up to approximately 1300 yards, but cannot defeat even 4 inch thick plate at 60deg obliquity when fired at point blank range."

Unfortunately, finding a link like that for 20 pounder ammunition is proving extremely difficult. Nonetheless, I do believe that 20 pounder will have trouble defeating T54 hull armor above 400 meters at best.

[dmnt]

This is a rather good read on physics of kinetic energy projectiles:
http://ciar.org/shotmagnet/Armor%20a...rojectiles.pdf

However, they're testing modern, 105-140 mm KE penetrators. Old ammunition might have been worse and glanced off or broken easier by slanted armor.

I could try and find if there's any material in Finnish related to this gun. Finns have a tendency of keeping all the records somewhere and then unclassifying them. However, I suspect that the issue of slanted armor effectiveness from gun to gun will provide way too complex for the game and this will be mostly an academic exercise.

[IronDuke99]

[quote=Aeraaa;835053]"(source: WW2 ballistics armor and gunnery by Lorrin R. Bird and Robert D. Livingston pages 30-31, although it speaks mainly about 17 pounder, 20 pounder wasnt much different)."

A late model 17 pdr fired APDS at 1,204 mps. (3,950 ftps) giving 275 mm of penetration at 100 mts and 162 mm of penetration at 3,000 mts.

The 20 pdr fired APDS at 1,465 mps (4,810 ftps) giving penetration of 300mm at 100 mts and about 195mm at 3,000 mts.

(Worth noting that the 20 pdr APDS round had roughly twice the penetration of a German 88mm AP round).

So far as I'm aware most armour penetration tables work on the basis of a 50% chance of penetration of a given thickness of armour at a given range ( but I was never a Tanker).