Getting the best mileage from the squeeze-bore guns? (1 Viewer)

[tomo pauk]

The almost 400m/s performance doesn't show up until late in the war.

It does not?

A substitute for the taper bore guns needs to be ready in 1940/early 41.

Covered in the post #42 here, at least for the 28/22.
No 42 mm type. The 47mm and French 75mm get the adapter.
Historical 75/55 is also never made, but the adapters for the 75mm ATG and tank guns are made, gets them to the Panther's level of AP performance with the appropriate ammo. Not for all and any such a gun, but certainly in the hundreds in 1942.

The IG 18's first HEAT shell was the one that had 260m/s velocity and had the 45mm at 30 degree performance. Used a powder charger of 71g.
It took a powder charge of 100g to get to 345m/s. Use of the longer barrel on the IG 37 may have made up the difference to 389ms (or higher) and there is no technical reason why a longer barrel could not have been used in 1940/41.

I've linked to the IG 37 article. That gun used same ammo that the Pz IVD or the -IIIN used, and not what the IG 18 used.

I am liking the Czech 4.7cm gun more and more.

You don't say

 

[Shortround6]

It does not?

Since the IG 37 doesn't seem to show up until 1944 I would appreciate any reference that says otherwise.
This just when it seems to have shown up, not that it could not have been done before.

I've linked to the IG 37 article. That gun used same ammo that the Pz IVD or the -IIIN used, and not what the IG 18 used.

The IG 37 sources can't seem to agree with themselves, let alone each other.

7.5 cm Infanteriegeschütz 37 - Wikipedia

en.wikipedia.org

says that the IG 37 used 75 x 89 mm R ammo while the gun in the PZ IV used 75×243mm R (?).

I have two of the books listed in sources of the Wiki article. The first book doesn't give the length of the cartridge case or the powder charge/s and only gives the MV of the standard HE shell. My copy of the book makes no mention of the HEAT round.
The 2nd source listed doesn't give details of specialty projectiles, just one velocity to cover everything, sometimes even different barrel lengths. But lists the short cartridge in the IG 37/42 and not the tank gun cartridge.
3rd source is the one I am using most of the time and I checked and I have the 2002 edition which is the one that is listed and I cannot find a 385ms velocity in the sections on the IG 18, IG L/13, IG 37 or IG 42.
However IG 37 was able to use a 100G charge to propel the standard 6kg HE shell at 280ms instead of the 210ms out of the IG 18. This may have been the charge (100g) that the IG used to get 345ms out of it's shorter barrel with the 3.05kg HEAT shell. Maybe it could have been done earlier if they had built the longer barrels and muzzle brakes earlier.
This book claims the IG 37 and IG 42 used the same ammo as the IG 18.
There are a couple of possible sources of confusion.
The Geb K 15 (old Czech mountain gun) fired a 4.5kg HEAT shell and perhaps there is some confusion.
The Geb G 36 (standard German mountain gun) fired a 4.4kg HEAT shell at 390m/s using charge 4 and not the max charge 5. In part due to recoil problems.

While trying to research this further I found the Soviet 76 mm regimental gun M1943 which is basically a short 75mm gun on a Soviet 45mm AT gun carriage and since the soviet 45mm AT gun carriage is pretty much the German 3.7cm AT carriage????
It is supposed to use a 76.2 × 167 mm R cartridge

at

76-mm-Regimentkanone M1943 – Wikipedia

de.wikipedia.org

I also found a trajectory chart for the earlier 76 mm regimental gun M1927 which used the same ammunition on this website.

76 mm HEAT Instructions

A blog about World War II era archive documents, primarily dealing with armoured warfare.

www.tankarchives.com

The trajectory column is giving the max high of the shell on the path to the target.

You can judge for yourself how practical some of the ranges were.

German Projectiles - 75mm Projectiles

German Projectiles H.E. Projectile Type 34, 75mm German Designation: Sprgr. Patr. KwK (34) (Spr...

ww2data.blogspot.com

has a cutaway and information of the HEAT round for the IG 18 but no performance figures for either penetration or velocity/range.
The design certainly looks like an early one. There was supposed to a 2nd design but penetration not much better.

Hope this helps.

 

[tomo pauk]

Since the IG 37 doesn't seem to show up until 1944 I would appreciate any reference that says otherwise.
This just when it seems to have shown up, not that it could not have been done before.

You were inquiring about the 37mm pak and what to do with it. The IG 37 was perfectly doable already pre-war.

The IG 37 sources can't seem to agree with themselves, let alone each other.

You are right. I was wrong saying that the IG 37 used the same ammo as the Pz-IVD did.

The towed gun that was using that ammo was the Pak 50, or basically the out-bored out-bored Pak 38 that also gotten a good part of it's barrel chopped off. That ammo/gun combination would've over-stressed the carriage of the Pak 36.

I have two of the books listed in sources of the Wiki article. The first book doesn't give the length of the cartridge case or the powder charge/s and only gives the MV of the standard HE shell. My copy of the book makes no mention of the HEAT round.
The 2nd source listed doesn't give details of specialty projectiles, just one velocity to cover everything, sometimes even different barrel lengths. But lists the short cartridge in the IG 37/42 and not the tank gun cartridge.
3rd source is the one I am using most of the time and I checked and I have the 2002 edition which is the one that is listed and I cannot find a 385ms velocity in the sections on the IG 18, IG L/13, IG 37 or IG 42.
However IG 37 was able to use a 100G charge to propel the standard 6kg HE shell at 280ms instead of the 210ms out of the IG 18. This may have been the charge (100g) that the IG used to get 345ms out of it's shorter barrel with the 3.05kg HEAT shell. Maybe it could have been done earlier if they had built the longer barrels and muzzle brakes earlier.
This book claims the IG 37 and IG 42 used the same ammo as the IG 18.

IG 18 ammo was fired with up to 70+g of propellant. The 100g propellant charge on the IG 37 will indeed require for a longer barrel to take advantage of that.

While trying to research this further I found the Soviet 76 mm regimental gun M1943 which is basically a short 75mm gun on a Soviet 45mm AT gun carriage and since the soviet 45mm AT gun carriage is pretty much the German 3.7cm AT carriage????
It is supposed to use a 76.2 × 167 mm R cartridge

One might see from where the Germans gotten the idea for the Pak 50...
Trying to see just how much the carriage of their light AT guns can handle would've paid good dividends to the Germans. Even if the gun from the Pz-IV does not fit conveniently on the carriage of the 37mm pak, it might've fit on the carriage of the Czech 47mm. So basically they might've gotten a good 47mm to weight just under 500 kg, and the short 75mm that can do close to 500 m/s with HEAT while weighting under 750 kg in the firing position. No exotic materials needed, and the reasonably capable guns are basically free, or they cost a fraction of the cost of a bespoke gun.

 

[tomo pauk]

Germans spent a pretty penny on the ammo for the 7.9mm anti-tank rifle, the thing being here that projectiles were mostly tungsten. About 510 thousand of rounds was present in their inventories already by May 1st of 1940. Even at just 10 grams a round (my assumption), that works to 5100 kg of tungsten. By June 1st of 1941, and despite the use in 1940, that balooned to more than 2.6 millions of rounds. Heer received in July of 1941 almost 740 000 these rounds.
They could've just go with a 13mm AT rifle (say, spin-off from the ww1 stuff) instead of the Pzb 38 & 39, use hardened steel ammo and get to the same penetration values; stick a good muzzle brake on it and there it is. Saves them tons of tungsten.

The 28/22 ammo count went to almost 350 thousand by June 1st '41; July saw more than 170 000 of that ammo received. I'm not sure about the HE/APCR ratio.

 

[Shortround6]

Germans spent a pretty penny on the ammo for the 7.9mm anti-tank rifle, the thing being here that projectiles were mostly tungsten. About 510 thousand of rounds was present in their inventories already by May 1st of 1940. Even at just 10 grams a round (my assumption), that works to 5100 kg of tungsten. By June 1st of 1941, and despite the use in 1940, that balooned to more than 2.6 millions of rounds. Heer received in July of 1941 almost 740 000 these rounds.
They could've just go with a 13mm AT rifle (say, spin-off from the ww1 stuff) instead of the Pzb 38 & 39, use hardened steel ammo and get to the same penetration values; stick a good muzzle brake on it and there it is. Saves them tons of tungsten.

Quite true. The Core for the 75/55 ammos was just about 2lbs so roughly 900 times what your estimate of the 7.9mm core? Not going to argue about a few percent or even 10%.
The 7.9mm AT rifles was one of those expensive toys. The early non Tungsten core round was the one that had the tear capsule inside. Difficulty of manufacture was????
effect in combat was zero. None of the troops that survived getting hit by it in the vehicles ever reported any effects.
The PzB 38 heavy and overly complicated for the intended use.

When fired the barrel moved for about 9cm and then Breech block unlocked and dropped, the cartridge case was automatically ejected and the Breech block held open. Gunner (or assistant) feed a new round into the breech, Gunner release a catch and the breech rose while the barrel returned to firing position. All very clever but expensive to make and prone jamming when dirty. Replaced by the PzB 39 where the gunner pulled on the pistol grip to to drop the breech block to eject and reload. Saved about 3.5kg and lot of machining.

The 28/22 ammo count went to almost 350 thousand by June 1st '41; July saw more than 170 000 of that ammo received. I'm not sure about the HE/APCR ratio.

You will get little argument. While the special troops may have wanted a special AT gun (rationale) I don't think the 28/20 really delivered. And the HE round was an evil joke. Delivering 5g of HE it makes a single shot 20mm look good and with each HE round fired the very expensive barrel is getting nearer to the end of it's life.
Give the special troops some Solothurn S18-1000 guns and call it a day and save the Tungsten.