Jump to content

Specific event: T-34(76mm) vs PIV H (late)


Recommended Posts

It's not just possible. It's almost a certainty when you factor in the exact properties of the impacting projectile.

As mentioned earlier, the 76.2mm shell vastly overmatches a 20mm thick plate (thickness/diameter ratio = .2625). When struck by 76.2mm APBC, a 20mm plate angled at 70.5° from vertical resists equivalent to 26.9mm. Factor in 95% armor quality for the Pz IV H (per CMBB) and the armor resistance is 25.5mm.

EDIT: Wrong value. See below.

Link to comment
Share on other sites

  • Replies 77
  • Created
  • Last Reply

Top Posters In This Topic

It's not just possible. It's almost a certainty when you factor in the exact properties of the impacting projectile.

As mentioned earlier, the 76.2mm shell vastly overmatches a 20mm thick plate (thickness/diameter ratio = .2625). When struck by 76.2mm APBC, a 20mm plate angled at 70.5° from vertical resists equivalent to 26.9mm. Factor in 95% armor quality for the Pz IV H (per CMBB) and the armor resistance is 25.5mm.

Could you specify for me how you get the 26.9mm ? :)

Link to comment
Share on other sites

T x F x (T/D)^G

T= armor thickness

T/D= thickness/diameter ratio (armor thickness/projectile diameter)

A= angle of impact

F=2.71828^(0.03723 x 1.06033^A)

G= -3.3667 + 0.07411 x A

something wrong?

T=20mm

T/D= 20mm/76,2mm=0,26247

A=70.5°

F=2,71828^2,31466=10,12147

G= -3.3667 + 5,224755 = 1,858055

T x F x (T/D)^G = 20mm x 10,12147 x 0,26247^1,858055

= 20 x 10,12147 x 0,08329 = 16,86 mm

16,86mm is not your 26,9mm....

Did i something wrong?

EDIT: You answered while i was writing this.

Thank you for the information ! :)

Link to comment
Share on other sites

Note that the thickness and angle of that plate is not consistent for all Pz IV models. On the ausf G it is 25mm thick @ 73°, which translates to equivalent resistance of 33.8mm (T/D = .3281 and 71.5° angle vs. 76.2mm APBC). So you can see how much the overmatching projectile affects the resistance where a 5mm increase in armor thickness doubles the effective resistance. But it will still penetrate ;)

53appendix.jpg

Link to comment
Share on other sites

Note that the thickness and angle of that plate is not consistent for all Pz IV models. On the ausf G it is 25mm thick @ 73°, which translates to equivalent resistance of 33.8mm (T/D = .3281 and 71.5° angle vs. 76.2mm APBC). So you can see how much the overmatching projectile affects the resistance where a 5mm increase in armor thickness doubles the effective resistance. But it will still penetrate ;)

I heard about the overmatching issue... Could not imagine that it can have such a tremendous effect... thank you again.... :)

Do you have a hard copy of the book or a scan?

Link to comment
Share on other sites

Question for all of you penetration grogs: one issue which has not come up is elevation differential, if any, eg, whether the T34 had an elevation advantage over the PIV--presumably that would also affect the penetration calculations by changing the angle of impact?

Link to comment
Share on other sites

Admittedly, I'm only skimming through all this since I can't be bothered to do math at 5 am when I just woke up, but it seems to me that people are still not taking into effect that angle of trajectory for the shell.

It's not hitting from straight ahead, it is hitting from slightly above due to the 1500m range trajectory.

Thus negating alot of that 70-75 degree angle you are using.

Link to comment
Share on other sites

Admittedly, I'm only skimming through all this since I can't be bothered to do math at 5 am when I just woke up, but it seems to me that people are still not taking into effect that angle of trajectory for the shell.

It's not hitting from straight ahead, it is hitting from slightly above due to the 1500m range trajectory.

Thus negating alot of that 70-75 degree angle you are using.

As previously mentioned, it does not negate "alot" of the angle of impact. And that small amount has been factored in.

Link to comment
Share on other sites

Question for all of you penetration grogs: one issue which has not come up is elevation differential, if any, eg, whether the T34 had an elevation advantage over the PIV--presumably that would also affect the penetration calculations by changing the angle of impact?

Sure it would. But only the OP would know.

Link to comment
Share on other sites

As previously mentioned, it does not negate "alot" of the angle of impact. And that small amount has been factored in.

Where was this mentioned? I must have missed it?

(and when playing CMRT at those distances, it does seem like it IS a significant angle actually)

EDIT: Nevermind, found it:

The angle of decent for Soviet 76mm at 1500 meters would be around 1.5 degrees, so that is not really a major factor.

The problem with single events like this is that we don't know for sure if CMx2 models weak point penetrations. We do know that there is no weak point penetration hit text so the only way to find out if there is a problem is further testing.

But if you look at the video I've uploade you'll see what appears to be far more than 1.5 degrees angle on that shell...

Link to comment
Share on other sites

Just made a quick movie to show what I mean by "significant angle".

Just a quick setup in CMRT with a T-34 firing on a panzer IV (G, but for these purposes it doesn't matter) at exactly 1500 meters.

You'll see that the angle is rather large after all (not as visible from the PzIV's view, but very visible from the T-34's view).

Here:

Ps. The kill shot was almost exactly where the OP had his.

EDIT: It is interesting to note that at 1500 meters, the ELITE T-34 took more than a minute on average to spot, or rather re-spot, the tank it had already fired upon before. With no terrain around and no other significant targets.

Link to comment
Share on other sites

Where was this mentioned? I must have missed it?

Page 1:

The angle of decent for Soviet 76mm at 1500 meters would be around 1.5 degrees, so that is not really a major factor.

Note that this is an estimate. I used the number for US 75mm APCBC since I had that number handy and it is ballistically similar enough to Soviet 76mm that the difference will not be off by more than a few tenths of a degree. If anything the 76mm may have a slightly flatter trajectory as it has a higher muzzle velocity.

Link to comment
Share on other sites

Page 1:

Note that this is an estimate. I used the number for US 75mm APCBC since I had that number handy and it is ballistically similar enough to Soviet 76mm that the difference will not be off by more than a few tenths of a degree. If anything the 76mm may have a slightly flatter trajectory as it has a higher muzzle velocity.

For the F-34 the muzzle velocity is 655m/s from what I remember.

BTW. did you miss my other post and my video?

Link to comment
Share on other sites

For the F-34 the muzzle velocity is 655m/s from what I remember.

Yes. And the muzzle velocity of the US 75mm M3 is 619m/s.

BTW. did you miss my other post and my video?

I watched the first half. You can't measure angle using that video but it does not appear to large at all to my eyes.

Link to comment
Share on other sites

-Interessting was that the kill shot seems to be closely the same like my kill.

-Further i ask myself if the hit decals are exact because someone said they are not.

-For me (in my game) the impact angle looked not small either....but it is hard to measure....better calculate....

nevertheless it seems not to be important for the outcome due to Vanir´s mentioned reference of the extreme bad overmatch-behaviour of 20mm plates.

I really thought ~70° is such a hard match for a round.....not only geometric wise....because of the less effectivity of the round at big angles too (cause by diverted impluse and misforming of the shell).

But these 20mm destroy the whole effect :(

-Would be interessting to know from where Bafflefront got his ballistic/trajectory formula for all weapons.

-BTW.: I always read for the F-34 a start velocity of 680 m/sec.

Link to comment
Share on other sites

-BTW.: I always read for the F-34 a start velocity of 680 m/sec.

It seems the HE shells have a velocity of that.

Odd that the AP shells have a slower velocity overall :/ (of course, the APCR has 965).

On the other hand, I just used wikipedia as a quickie source (blasphemy, I know)

Link to comment
Share on other sites

T x F x (T/D)^G

T= armor thickness

T/D= thickness/diameter ratio (armor thickness/projectile diameter)

A= angle of impact

F=2.71828^(0.03723 x 1.06033^A)

G= -3.3667 + 0.07411 x A

Hello Vanir,

would like to get further information about the formula.....

The formula has obviously limitations......... you may only be allowed to use this formula under special conditions.

Why do i think that? you may ask....here comes the answer:

For example:

Try to use a 200 mm thick armor plate against this 76,2 mm round and tell me what the formula calculates as result.

Here the results:

at impact-angle of:

0°= 8,06mm :eek:

10°=16,97mm

20°= 36,6mm

30°= 82,34mm

40°=199,91mm

50°= 556,56mm

60°=1981,59mm

70°=10974,68mm

80°=134420,36mm

89,9°= 6520086,52

Sorry...but the Elefants should then have died like flys when they got shot by T-34/76 tanks and only had an equivalent armorprotection of 8-16mm steel instead of 200mm....:D

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...