The Panzerabwehrwerfer 600

While I have quite a bit on the operation of this somewhat obscure anti-tank gun does anyone have a detailed development history on it. It was a Rhinemetall product that came into service in late 1944.

 

80mm PAW 600
Type: antitank gun Nationality: Germany
A really innovative solution for antitank cannons. The problem was the ever increasing weight of the antitank weapons, necessary to pierce ever thicker armor plates. Shoulder weapons, like the Panzerfaust or the bazooka, had not enough range and recoilless guns lacked accuracy. Rheinmetall proposed in 1944 the "high low pressure" system. The idea was to ignite the propelling charge in a reinforced chamber and let the gases escape from it only progressively, so that there was no peak of pressure in the barrel (1). The propulsion was more regular than with the conventional system and the barrel could be lightened since it had to resist a lesser stress.
The barrel was smooth and the projectile, inspired by a mortar bomb (2), was fin stabilized. It was either antipersonnel or shape charge, which gave the weapon a formidable antitank capability. Appearing late 1944, only a limited number could reach the frontline. Despite the interest the principle arose, it was not widely used after the war.
The gun had no variant, but its designation changed after tests on the frontline (from "80 mm PAW 600" to "PWK 8H63"), leading the allies to believe that a new model had come out.
(1) the maximum pressure was one ton par square centimeter in the chamber but half as much in the barrel.
(2) hence the caliber: the standard mortar of the Wehrmacht was a 81 mm
Built by Rheinmetall-Borsig AG
Other designation(s): 80mm Panzerabwehrwerfer 600, PAW 8H63, PWK 8H63
Upper: 80mm, Pak

Various
Caliber: 81 mm
Length: 2.95 meters

Production
Production: 260 examples
Performances
Muzzle velocity: 419 meters per second
Range: 6 197 meters

Here's some stuff I found online TA, hope it helps.

 

And the net picture 8cm Panzerabwehrwerfer 600

 

That's the one Kai, I couldn't post it though, it wouldn't let me, lol.

 

Just to add a couple of bits to OTF's material :

The 260 guns were produced between December 1944 and March 1945.The projectile looked very similar to the standard German mortar rounds. Krupp were also developing a 10.5cm version at the very end of the war. Known as the PWK 10H64, the prototype was stillborn.

The photo shown above is of the weapon at the Aberdeen Proving Ground.

 

I knew quite a bit about this weapon technically, what I really need is when did Rhinemetall start development of it. When did they come up with the concept of the high-low pressure gun system?
As for the actual round fired, it was 81.4mm in diameter. The cartridge was a cut down 105mm shell casing on top of which a thick steel plate with a series of venturi holes in it. The "bomb" (for want of a better term) was a modified 81mm mortar round with a shaped charge warhead. It was attached to the 105 cartridge by a spigot that had a shear point on it.
When fired, the gases of the explosion were primarily trapped in the 105 cartridge and only about a third escaped through the venturi to shear the pin and fire the bomb. It was accurate enough to put 9 out of 10 rounds in a 1 x 1 meter square at 500 meters. Penetration was 145 mm; a performance sufficent to take out virtually any tank of the day.