Early HEAT Ammunition

Discussions on the vehicles used by the Axis forces. Hosted by Christian Ankerstjerne
User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#31

Post by Mobius » 27 Oct 2016, 21:10

Yoozername wrote:
1. 75mm/L24 HL round Training @ 1000m = 92%; @ 1500m = 61%.
2. 75mm/L48 HL/C round Training @ 1000m = 85%; @ 1500m = 42%.
Basically you are saying that the L24 (KWK 37) had not only superior accuracy over the L48 (KWK 40), but actually acceptable accuracy that far exceeds the Germans own guidelines for using the ammunition.

http://www.panzerworld.com/tank-combat-firing-methods
I'm not saying that at all.

On Panzerworld 75mm/L48 table per Accuracy of Pzgr 39 'Training' @ 1500m is 77%. So 77% > 61%. Now the Firing Methods page has without range misjudgment accuracy as 75%. 75%>61%
[Edit] Correction - the link's Firing Methods is for the Pak 40 (75mm/L46) not 75nn/L48. So that may be the MV of 790m/s which would mean it is less accurate than the L48 (MV=750m/s). Something to digest.]
Last edited by Mobius on 28 Oct 2016, 16:48, edited 4 times in total.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

Re: Early HEAT Ammunition

#32

Post by Yoozername » 28 Oct 2016, 00:42

I will say this as clearly as possible...There is no way a short L24 gun is going to have greater accuracy firing a HL/X projectile than a longer L48 gun. Even if the velocities are the same. I think you may have the numbers mixed up?


User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#33

Post by Mobius » 28 Oct 2016, 05:41

Yoozername wrote:I will say this as clearly as possible...There is no way a short L24 gun is going to have greater accuracy firing a HL/X projectile than a longer L48 gun. Even if the velocities are the same. I think you may have the numbers mixed up?
It's not my numbers, it's the German documents numbers.
You can't prove anything unless there is some data. Maybe somewhere there is an overlap of a shorty firing HL/A,B or C for accuracy. Right now I'll go along with the data that is. For my purposes the dispersion difference of 0.6/0.8 of the HL and 0.7/0.9 on the HL/Cs is pretty insignificant. With a 15% mean estimation error the HL would have a 58% chance of a hit on a stationary T34 at 500 m while the HL/C would have a 57.3% chance of a hit.

Paul Lakowski
Member
Posts: 1441
Joined: 30 Apr 2003, 06:16
Location: Canada

Re: Early HEAT Ammunition

#34

Post by Paul Lakowski » 28 Oct 2016, 19:56

Yoozername wrote:I will say this as clearly as possible...There is no way a short L24 gun is going to have greater accuracy firing a HL/X projectile than a longer L48 gun. Even if the velocities are the same. I think you may have the numbers mixed up?
do you have any figures ?

User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#35

Post by Mobius » 28 Oct 2016, 20:19

Christian Ankerstjerne wrote:
8,8 cm Pzgr. 39/43
500 m: 0.2x0.2 (1:1)
1000 m: 0.3x0.5 (1:1.7)
1500 m: 0.5x0.7 (1:1.4)
2000 m: 0.7x0.9 (1:1.3)
2500 m: 0.9x1.1 (1:1.2)
3000 m: 1.0x1.4 (1:1.4)

4,7 cm Pzgr. 36 (t)
500 m: 0.2x0.2 (1:1)
1000 m: 0.4x0.4 (1:1)
1500 m: 0.4x0.8 (1:2)
2000 m: 0.6x1.4 (1:2.3)
2500 m: 0.8x2.2 (1:2.8)
3000 m: 1.2x3.4 (1:2.8)
You know Christian, it would be nice if this information was also available on your panzerworld website. I didn't even see mention of the 4.7 cm (t) there. If the dispersion is available at 500m intervals could you post the impact velocity as well?

User avatar
Christian Ankerstjerne
Forum Staff
Posts: 14028
Joined: 10 Mar 2002, 15:07
Location: Denmark
Contact:

Re: Early HEAT Ammunition

#36

Post by Christian Ankerstjerne » 28 Oct 2016, 20:32

Mobius wrote:You know Christian, it would be nice if this information was also available on your panzerworld website. I didn't even see mention of the 4.7 cm (t) there. If the dispersion is available at 500m intervals could you post the impact velocity as well?
I do plan to put it all up there eventually, but there's so much interesting material that it does take time. All the gun tables are dispersed at 100 m, with information on range, gun elevation, 'sideways movement' (Seitenverschiebung, in mils, not entirely sure about this), travel time, dispersion in meters, terminal velocity, and descend angle. Posting it in 500 meter increments makes a bit more sense, as the tables will otherwise be quite massive.

The terminal velocity for the 4,7 cm Pzgr. 36 (t) is:
500 m: 662 m/s
1000 m: 558 m/s
1500 m: 466 m/s
2000 m: 390 m/s

I noticed that I posted the dispersion data for the 4,7 cm Sprgr. 36 (t) (the name is corrected by hand). The Pzgr. data is:
500 m: 0.2x0.2 (1:1)
1000 m: 0.4x0.4 (1:1)
1500 m: 0.6x0.8 (1:1.3)
2000 m: 0.8x1.4 (1:1.75)

It's quite interesting that the dispersion is greater for the higher-velocity round.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

Re: Early HEAT Ammunition

#37

Post by Yoozername » 28 Oct 2016, 21:03

The first iteration, the HL (4.5 kg), has a blunt nose. The HL/X (HL/A 4.4Kg, HL/B 4.75Kg, HL/C 4.8Kg) all have an aerodynamic 'cap', and for most purposes, they are basically the same with a weight difference (which seems to have been factored in the propellant weights) and the same velocities. In fact, most weapons of the 75mm-76.2mm that the Germans manufactured a HEAT round for have a velocity of 450 m/s. The infantry guns were less , I believe. The 88mm had a 600 m/s, so I suppose the fusing would work at that velocity.

They all have one bad physical characteristic, that is they all have a axial center of mass (COM) WAY towards the rear. I would estimate it to be as far back as slightly forward of the driving band. The HL/C would have the COM a little forward than the A and B, but not much. Take a water bottle and fill it with an inch of water (standing up in freezer) and freeze it, now try and throw it in a spiral (ice facing the rear),. Something like the HE round would even be much better as far as having a COM towards the middle of the round.

The 'training' numbers, I presume, mean a known range and a zeroed weapon. The Panzerworld page regarding tank combat firing methods have these recommendations:
The above facts point to begin training anti-tank gunners and tank gunners in artillery firing methods. The key differences for the above-mentioned anti-tank gunners and tank gunners are:

The gunner always uses the same aiming point.
The commander provides range commands, also against moving targets, and determines the range to the target from the impact.
In regards to very flat trajectories, it is sufficient to make aiming marks at 200 meter intervals for the anti-tank gun and tank gun. Minor corrections can then be made in the usual manner by changing the aiming point.

At short distances, with sufficiently flat trajectories and large target areas, the firing method can be kept, i.e., with the approximated or measured distance being corrected by adjusting the target to the target width or height.

The task now is to find the border between the two methods, which differ according to ballistics and ammunition.

In regards to the 200 meter marks, it appears appropriate that the limit whereby raising or lowering the flight path along the height of the tank (on average two meters) gives a change in distance of less than 200 meters. This is approximately the same range at which the target area change by less than 200 meters, e.g:

Shot Maximum range
7,5 cm Pak/KwK 40
Pzgr. 39 1200 m (~95%)
Pzgr. 40 1400 m (~70%)
Gr. 38 Hl/B 600 m (~97%)

kwk 37 Accuracy Training only
Round Range
100 m 500 m 1000 m 1500 m
K Gr rot Pz 100% 100% 98% 74%
Gr 38 Hl 100% 100% 92% 61%

kwk 40 Accuracy Training only
Accuracy Training only
Round Range
100 m 500 m 1000 m 1500 m
Pzgr 39 100% 100% 99% 77%
Pzgr 40 100% 100% 95% 66%
Gr 38 Hl/C 100% 100% 85% 42%

The L24 gun has to accelerate the round in a shorter period of time than the L48, not only that it also gets 'spun-up' quicker. In other words, it is pulling more Gs to get it out of the barrel. Comparing the HL to the HL/C, the HL/C weighs more. looking at the L24 training accuracy, there is very little difference in the accuracy at 1000 meters. 98% vs. 92% and the K Gr rot weighs 6.8 Kg vs. 4.5 Kg? It just strikes me as odd that the 1000m accuracy is better with the L24 than the L48 (maybe L43). Also, the Germans recommend a 600 meter range as a SOP. I get that you are using the Germans numbers, but it just doesn't square with that report (the Germans were more than likely using HL/B in many weapons in Sep 43). The Pak 40, for example, only 'started' with the HL/B.


Hmmmmm. To be continued.

Edit: Just an interesting note is that I do not see 'training' ammunition (Ub) as far as HEAT for many of these weapons. Also, the AP/HE/HEAT weights are different but I suppose the German sights just used the closest matching velocity in many cases.

User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#38

Post by Mobius » 28 Oct 2016, 23:20

Christian Ankerstjerne wrote: I noticed that I posted the dispersion data for the 4,7 cm Sprgr. 36 (t) (the name is corrected by hand). The Pzgr. data is:
500 m: 0.2x0.2 (1:1)
1000 m: 0.4x0.4 (1:1)
1500 m: 0.6x0.8 (1:1.3)
2000 m: 0.8x1.4 (1:1.75)

It's quite interesting that the dispersion is greater for the higher-velocity round.
I take it the pzgr shell is the higher velocity because the Sprgr. 36 has no velocity listed.

So is all this data in a book or separate papers?
Last edited by Mobius on 28 Oct 2016, 23:39, edited 1 time in total.

User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#39

Post by Mobius » 28 Oct 2016, 23:37

Yoozername wrote: The L24 gun has to accelerate the round in a shorter period of time than the L48, not only that it also gets 'spun-up' quicker. In other words, it is pulling more Gs to get it out of the barrel. Comparing the HL to the HL/C, the HL/C weighs more.
So how many twists are in the L24 barrel? The US 76mm gun M62 AP lost less velocity when it went from M1A1 1:40 twists to M1A2 1:32 twists.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

Re: Early HEAT Ammunition

#40

Post by Yoozername » 29 Oct 2016, 00:44

I believe the L24 might have had a progressive twist, but I will have to find where I read that. The L43 also had a progressive twist, and so did the first batch of L48, but this was changed to a constant rate twist for the rest of the war. As far as RPM of the projectile, it is actually the final twist rate near the end of the barrel that matters.

IF the L24 shot out the projectile at the same RPM as the L48, THEN the L24 would need a tighter twist rate, perhaps twice as much as the L48.

User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#41

Post by Mobius » 29 Oct 2016, 00:55

Yoozername wrote: final twist rate near the end of the barrel that matters.

IF the L24 shot out the projectile at the same RPM as the L48, THEN the L24 would need a tighter twist rate, perhaps twice as much as the L48.
The way they do twist rate for artillery is twist rate [edit] per caliber. If the final twist rate is what counts then at the end of the barrel is what counts. The MV is the same so any difference in twist rate could result in better stability.
Last edited by Mobius on 29 Oct 2016, 01:50, edited 2 times in total.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

Re: Early HEAT Ammunition

#42

Post by Yoozername » 29 Oct 2016, 00:57

This might directly answer the OP...
Die deutschen Sturmgeschütze 1935-1945" by Wolfgang Fleischer

From July 1940 the 7.5 cm Granatpatrone 38 was available. With this could 40 mm of armour be penetrated, independently of range. Thus the StuG had the chance to achieve occasional penetrations of the front and sides of the T34. The chance to damage a KW tank was even less.

--

In the end of 1941 improved HL grenades were delivered. First came the HL/A, then the HL/B with, respectively, 70 and 75 mm penetration. Now the tank hunting could again be conducted under 1500 meters more successfully. Between four and six shots were still required to achieve a hit.

"Die deutschen Panzerjägertruppe 1935-1945" by Wolfgang Fleischer

(late war) As a rule HL ammunition shall be used unless the situation absolutely requires the use of regular AP. Prime examples of such circumstances are at short distances, due to the excessive force of impact, and when faced with heavily armoured targets.
Good data shot...
Panzer Abt. 116 reported that after fighting 76 battles and moving 3020 km between 1 July 1943 and 31 January 1944 They had expended the following amount of 7.5 cm ammunition:

KwK40 HE: 4867

KwK40 AP: 1798

KwK40 HL/B:1237

KwK L/24 AP:39

KwK L/24 HL/B: 99
5th Pz. Div. reports in engagements between the 22 February to 20 March 1943.

7.5 cm KwK L/24:

1 KW-I, 6 T34, 1 T60, 4 T26, 1 Mark II, 4 Mark III, 1 Gen. Lee. Gr.38 HL/B has destructive effect when fired at ranges under 600 meters at the hull and rear of the KW-I. The T34 was also engaged by firing at the hull. Three to six rounds of Gr.38 HL/B were required to kill each enemy tank.

Gr.38 HL/B was seldom fired by the 7.5 cm KwK L/43 tanks. One to five rounds were reqiured to set an enemy tank on fire.

Yoozername
Member
Posts: 2615
Joined: 25 Apr 2006, 16:58
Location: Colorado

Re: Early HEAT Ammunition

#43

Post by Yoozername » 29 Oct 2016, 01:10

The way they do twist rate for artillery is twists per caliber. If the final twist rate is what counts then at the end of the barrel is what counts. The MV is the same so any difference in twist rate could result in better stability.
Are you trying to show that the L24 had a higher spin rate? That is, it would make the unbalanced HEAT rounds more stable somehow?

If one were to take a weapon, and using the same charge, fire the same projectile but use two different barrels, one with a higher twist rate, then I would expect the translational velocity to decrease somewhat in the higher rate twist. Why? Because there is angular energy put into the spinning projectile. There is no free energy.

User avatar
Christian Ankerstjerne
Forum Staff
Posts: 14028
Joined: 10 Mar 2002, 15:07
Location: Denmark
Contact:

Re: Early HEAT Ammunition

#44

Post by Christian Ankerstjerne » 29 Oct 2016, 01:47

Mobius wrote:
Christian Ankerstjerne wrote: I noticed that I posted the dispersion data for the 4,7 cm Sprgr. 36 (t) (the name is corrected by hand). The Pzgr. data is:
500 m: 0.2x0.2 (1:1)
1000 m: 0.4x0.4 (1:1)
1500 m: 0.6x0.8 (1:1.3)
2000 m: 0.8x1.4 (1:1.75)

It's quite interesting that the dispersion is greater for the higher-velocity round.
I take it the pzgr shell is the higher velocity because the Sprgr. 36 has no velocity listed.

So is all this data in a book or separate papers?
4,7 cm Sprgr. 36 (t)
500 m: 525 m/s
1000 m: 457 m/s
1500 m: 399 m/s
2000 m: 353 m/s
2500 m: 320 m/s

The numbers are from the firing tables, in this case H. Dv. 119/310.

User avatar
Mobius
Member
Posts: 645
Joined: 12 Jan 2005, 21:45
Location: Glendale, CA
Contact:

Re: Early HEAT Ammunition

#45

Post by Mobius » 29 Oct 2016, 02:06

Yoozername wrote:
The way they do twist rate for artillery is twists per caliber. If the final twist rate is what counts then at the end of the barrel is what counts. The MV is the same so any difference in twist rate could result in better stability.
Are you trying to show that the L24 had a higher spin rate? That is, it would make the unbalanced HEAT rounds more stable somehow?

If one were to take a weapon, and using the same charge, fire the same projectile but use two different barrels, one with a higher twist rate, then I would expect the translational velocity to decrease somewhat in the higher rate twist. Why? Because there is angular energy put into the spinning projectile. There is no free energy.
We had the same discussion back in 2012 at Matrix about APCR and AP.
I don't know internal ballistics, but I do know 100% of the energy from the charge is not transferred to the projectile. In which case the energy in the spin may be not exactly equal to the energy missing from the projectile's muzzle velocity.
Last edited by Mobius on 29 Oct 2016, 02:31, edited 1 time in total.

Post Reply

Return to “The Ron Klages Panzer & other vehicles Section”