Short barreled Pak 40

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Re: Short barreled Pak 40

#16

Post by jopaerya » 30 May 2009, 20:44

Hi Alain

I have also read in many books your version , but I never found or see any original information to prove this .
Waffen Revue are all based on first hand German information and all facts given by Peeved makes me to
change my opinion on this subject .

Regards Jos

Alanmccoubrey
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Re: Short barreled Pak 40

#17

Post by Alanmccoubrey » 30 May 2009, 21:23

Well, regardless of what it may say just look at the gun, all the parts are clearly Pak 40, breech, barrel and recoil slide beneath the barrel. The evry idea that a Pak 38 barrel had enough thickness in its walls to allow it to be rebored from 50mm to 75mm is actually a bit beyond belief.
Alan


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Re: Short barreled Pak 40

#18

Post by peeved » 31 May 2009, 00:16

The Pak 50 breech is quite obviously from a Pak 38 which can be seen comparing pictures 1.jpg and Pak38.jpg on page 1; Pak 40 e.g. had a much longer breech ring as shown at http://en.wikipedia.org/wiki/File:Pak40 ... i_rear.jpg , totally different operating lever etc.

Comparing the pic below showing both the Pak 38, 50 and 40 barrels in approximately same scale it can be seen that both the Pak 50 barrel and modified cradle have been moved forward, quite natural when trying to maintain trunnion balance with a shortened and bored out barrel. Comparing the Pak 38 and 50 barrel diameters in the pic also shows that reboring the 5 cm Pak to 7,5 cm appears not to have been beyond WW II German belief. After all the reboring affected the thicker breech end of the barrel which was rechambered to take a relatively low velocity (compared with the Pak 38) 7,5 cm cartridge.

Comparing the Pak 50 with Pak 40 IMO shows little support to your claim:
just look at the gun, all the parts are clearly Pak 40, breech, barrel and recoil slide beneath the barrel
In addition to the Pak 40 breech being quite different, its barrel is of larger diameter and its barrel contours are a poor match.

Markus

Edit: Just noticed that two pics last page; Pak50-1.jpg used in the composite below and the photo it's apparently drawn from, Pak50-5.jpg from the US intelligence report, are based on a reversed negative. That doesn't change the dimensions I used in the comparison above but downloaders might want to use the mirrored pics below.
Attachments
Pak38-50-40.jpg
Pak38-50-40.jpg (48.81 KiB) Viewed 3115 times
Pak50-1a.jpg
Pak50-1a.jpg (50.54 KiB) Viewed 3119 times
Pak50-5a.jpg
Pak50-5a.jpg (57.26 KiB) Viewed 3118 times

Alanmccoubrey
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Re: Short barreled Pak 40

#19

Post by Alanmccoubrey » 31 May 2009, 18:58

So you really think that the barrel of a 50mm gun was thick enough to allow it to be rebored by 50% ?
Alan

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Re: Short barreled Pak 40

#20

Post by peeved » 31 May 2009, 19:15

I'm quite convinced that it was feasible considering the fact that the guns AFAIK were rebored for the same relatively low-velocity and pressure ammo as the 7,5-cm-KwK 37 L/24 "Stummel". The captured Pak 50s don't seem to have suffered ill effects from test firing if any.

IMO a more adventurous German reboring effort was turning captured Soviet 7,62 cm AA guns into lightweight 8,8 cm Flaks.

Markus

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Re: Short barreled Pak 40

#21

Post by Alanmccoubrey » 31 May 2009, 19:44

Markus, The reboring on the Soviet Flak guns was only 10%. Where did you read that the ammo was from the L/24 ?
Alan

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Re: Short barreled Pak 40

#22

Post by peeved » 31 May 2009, 20:18

The reboring on the Soviet Flak guns was only 10%.
The 15% calibre increase in the 7,62/8,8 cm Flak conversion was relatively speaking small but the Soviet guns were rather lightly built in the first place and this was a HV to HV ammo conversion whereas the Pak 50 was a HV to LV one.
Where did you read that the ammo was from the L/24 ?
E.g. the "Organisations-Abteilung III des OKW" war-diary entry from WR 102 mentioned earlier:
On 1. 10. 1943 the Führer was introduced the 5-cm-KwK and Pak 38 rebored to 7,5 cm.
continued
Therefore the OKW orders that of the 5-cm-barrels in the area of Ob.West 1000 are to be rebored to use the 7,5-cm-LwK-L/24 ammunition.
The L/24 calibre is also mentioned in Speer protocols etc.

Also the Intelligence Report from 17th July 1945 quoted in WR 102 notes that the Pak 50 with barrel number R 272 had a range drum calibrated for 7,5-cm-Gr.Patr.38 and 7,5-cm-Gr.Patr.KwK (ammo types of the 7,5-cm-KwK L/24). Additionally the chamber length of 256 mm stemming from the report corresponds nicely to the 7,5-cm-KwK L/24 case length of 243 mm.

Markus

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Re: Short barreled Pak 40

#23

Post by Alanmccoubrey » 31 May 2009, 21:52

Does this WR 102 happen to say how many rounds the gun could fiore before the barrel melted ? The walls of the barrel can't have been more than a couple of mm thick, hoo hum !
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Re: Short barreled Pak 40

#24

Post by peeved » 31 May 2009, 22:17

Measuring from the retouched photo against known ordnance length of 2240 mm with muzzle brake I'd say the visible front end of the Pak 50 barrel is about 107 mm in diameter. That would still have left ca. 16 mm wall thickness around the thinnest point; more than e.g the 12,5 mm in the muzzle of 5-cm-KwK L/42. The Pak 50 muzzle also appears heavily hooped behind the muzzle brake. Sometimes a couple of mm appear adequate.
Markus

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Re: Short barreled Pak 40

#25

Post by Alanmccoubrey » 01 Jun 2009, 11:39

I do have to ask as well, just what the point of doing all that work to a Pak 38 to give it an inferior anti-tank capability ? The small increase in HE performance doesn't seem to be worth the effort. The idea of the Pak 50 was supposedly to provide a lighter gun with a similar a/t performance tro the Pak 40, the Pak 38 was already better than the KWK 37 so why do all that work reboring (which you will never convince they did) and rechambering ? All they needed to do was adjust the fittings to get a shortened Pak 40 barrel into the Pak 38 carriage. The Pak 50 as described by this WR 102 is a compleytely illogical waste of effort while the Pak 50 as described in Hogg's Artillery book and Lexikon der Wehrmacht is at least based on a bit of sense.
Alan

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Re: Short barreled Pak 40

#26

Post by jopaerya » 01 Jun 2009, 12:19

Hello

First I repected every one's opinion , but can you tell me the reason why a barrel of a shorted PaK 40 was placed on a
carriage of a PaK 38 and not just only to shorted the barrel of the PaK 40 and leave it on the carriage of the PaK 40 ,
this would save's a lot of manhours and workplaces in the last years of the war ?

Regards Jos

edit

Please see also this the PaK 37 later I.G. 37 fired as PaK Hohlladungen , so this could also be the case for the PaK 50

Von der Firma Krupp stammte die 510 kg schwere 7,5-cm-Pak 37. Das Provisorium stellte eine Kombination zwischen einem Infanteriegeschütz und einer Pak dar. In die Lafette der 3,7-cm-Pak wurden 1.800 mm lange Rohre vom Kaliber 7,5cm mit einer Länge von 1.800 mm eingebettet. Später wurden auch russische Beutelafetten benutzt. Bei einer v0 von 280 m/Sek. wurden Schußweiten bis 5.150 m erreicht. Die zur Panzerabwehr verwendete Hohlladungsgranate durchschlug mit ihren 0,5 kg Sprengstoff Panzerungen bis zu 85 mm bei einer v0 von 395 m/Sek. Im Mai 1944 stufte das Waffenamt die Geschütze als Infanterie-Geschütz 37 neu ein. Im Juni 1944 wurden die ersten 84 Waffen an die Truppe ausgegeben, bei Kriegsende waren noch 1.304 Waffen bei der Truppe. Die Waffen hatten einen Schwenkbereich von 60° und eine Rohrerhöhung von -5° bis +24°.

Info = Lexikon der Wehrmacht

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Re: Short barreled Pak 40

#27

Post by peeved » 01 Jun 2009, 16:11

Alanmccoubrey wrote:I do have to ask as well, just what the point of doing all that work to a Pak 38 to give it an inferior anti-tank capability ?
Only provided the Pak 38 was using PzGr 40 which became a no-no due to the tungsten shortage, 1943 being the last 5-cm-PzGr 40 production year. Hohlladungsgranate 38 C of the 7,5-cm-KwK 37/L/24 pierced 75 mm of armour at all distances which the 5-cm-PzGr 39 from a Pak 38 only matched at point blank ranges (as usual German penetration figures being given at an 60 deg. angle of impact). I guess the Germans were wrong in e.g. arming late production Pz IIIs with the 7,5-cm KwK 37 instead of the 5-cm KwK then and positive reports from the front regarding the change were erraneous also?
The small increase in HE performance doesn't seem to be worth the effort.
By Jingo, let's ditch the 155 mm guns (not worth the effort) and go back to 105 mm if only a small increase in HE performance results from an almost 200% weight increase; from the 1,96 kg 5-cm-SprGr to the 5,75 kg 7,5-cm-SprGr 34? :roll:
The idea of the Pak 50 was supposedly to provide a lighter gun with a similar a/t performance tro the Pak 40,
According to which primary source? The German contemporary view appears to have been the need to make use of old 5-cm barrels that were no more effective against enemy armour.
the Pak 38 was already better than the KWK 37
Penetration-wise compared to the Hohlladungsgranate 38 C only with PzGr 40 as noted before.
so why do all that work reboring (which you will never convince they did)
Some people will tend to believe the monkey... In this case I'd listen to the organ grinder.
and rechambering ? All they needed to do was adjust the fittings to get a shortened Pak 40 barrel into the Pak 38 carriage.
And get that Pak 38 breech block blown straight out. Or do you still believe that the Pak 50 had a Pak 40 breech despite photographical and numerical evidence to the contrary?
The Pak 50 as described by this WR 102 is a compleytely illogical waste of effort
If anything it was too little gun for the carriage which may have been the reason why it appears not to have been produced in quantity whereas the significantly lighter I.G. 37 conversion and its I.G. 42 derivative were well thought of and mass-produced although production never caught up with the demand. After all the somewhat instable 7,5-cm-Pak 97/38 conversion would've had a better ballistic performance on the Pak 38 carriage. E.g. would have made more sense to continue the Pak 97/38 conversions and ditch the Pak 38 uppers to coastal and land fortifications than produce the Pak 50.
while the Pak 50 as described in Hogg's Artillery book and Lexikon der Wehrmacht is at least based on a bit of sense.
The Pak 40 chop shop theory is based on little sense although it would have been a blast... Muzzle blast; merely wasting ballistical potential in a barrel about half the length of the one intended by the Pak 40 designers.

In fact Waffen Revue 102 asked several questions pertinent to the Pak 40 shortling theory:

Since the 7,5-cm-Pak 40 was manufactured until the end of the war (Hitler himself demanding increased production) and was urgently needed for installation in fortifications, SPGs etc.

1) Why would Pak 40 barrels be manufactured to be shortened?
2) Even if such barrels had been used is there any reason why the breech mechanism was altered. The Pak 40 breech was excellent and would have worked just as well with a shortened barrel.
3) Like Jos, WR also asked why a shortened Pak 40 would be put on a Pak 38 carriage which would have to be altered for that purpose.

Additionally why do you AOT ignore the Intelligence Report from 17th July 1945 quoted in WR 102 which makes it obvious that the Pak 50 didn't use Pak 40 ammunition?

Markus

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Re: Short barreled Pak 40

#28

Post by Alanmccoubrey » 01 Jun 2009, 21:13

I'm not ignoring the WR 102, I'm asking you why you think that the Germans went to all that trouble for something that was no better than the gun they wasted all the effort changing. I don't really think that any US int report can be called the organ grinder either ! Nor for that matter should you be calling Ian V Hogg a monkey !
Alan

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Re: Short barreled Pak 40

#29

Post by peeved » 01 Jun 2009, 21:40

Alanmccoubrey wrote:I'm not ignoring the WR 102, I'm asking you why you think that the Germans went to all that trouble for something that was no better than the gun they wasted all the effort changing.
As shown previously the 7,5-cm L/24 had a better AP and HE performance than Pak 38 (without PzGr 40) and the Germans obviously knew that. To repeat the quote from the Organisations-Abteilung III des OKW war diary from 3.10.1943:
2) 7,5-cm-Pak 50 (Pak 38 rebored)
a) Performance increase of the former 5-cm-Pak.
Anyhoo based on available information the Pak 50 remained experimental at a small scale so any effort expended was relatively minor. As noted before the gun was ballistically bantam weight for the carriage which may have been a contributing factor to the Pak 50 remaining experimental.

OTOH in 1942 the Germans were seriously contemplating wedding the 5-cm-KwK L/42 to ex-Soviet 45 mm AT gun carriages considerably lighter than the Pak 38 one. Since the L/42 was one of the guns considered for the 7,5-cm conversion it appears that a lighter 5-cm to 7,5-cm conversion than the Pak 50 would have been feasible.
I don't really think that any US int report can be called the organ grinder either ! Nor for that matter should you be calling Ian V Hogg a monkey !
The US intel report being a primary document which doesn't conflict with original German ones, carries more weight than the efforts of later writers who, based on info in WR 102 may have been mimicking (monkey see, monkey do) a mistranslation from the US report in Die deutschen Geschütze 1939-1945 by F.M. von Senger und Etterlin, first published in 1960. The mere fact that it is obvious to the naked eye that the Pak 50 barrel diameter and contours in addition to the breech are totally different from Pak 40 but similar to the Pak 38 should have convinced even laymen that the amputated Pak 40 theory was bogus even before the Waffen Revue revealed factual documents behind the gun development and tech data of captured examples.

Markus
Last edited by peeved on 03 Jun 2009, 13:32, edited 1 time in total.

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Re: Short barreled Pak 40

#30

Post by Spontoon » 03 Jun 2009, 06:08

I'm sure the reboring of 50mm A/T guns consisted not so much of boring them out, but of re-linering the outer casing of the barrel. This is what was done to the British 6 pdr. to 75mm conversion.

As far as Ian V. Hogg and monkeys are concerned, I have highlighted pages of gross errors in his books in my collections!

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