The PAW 600 was a lightweight anti-tank gun that used the high-low pressure system

High-Low System

The High-Low system also referred to as the "High-Low Pressure system", the "High-Low Propulsion System", and the "High-Low projection system", is a design of cannon and antitank launcher using a smaller high-pressure chamber for storing the propellant...

 to fire hollow charge warheads. It was used operationally by Wehrmacht

Wehrmacht

The Wehrmacht – from , to defend and , the might/power) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the Heer , the Kriegsmarine and the Luftwaffe .-Origin and use of the term:...

in 1945 in small numbers.

Background

By 1943 the German army was faced with various problems with regards their existing anti-tank gun designs. They had started the war with the 3.7 cm Pak 36 which had the advantage of being very light at 328 kg. so that it could be moved a reasonable distance by hand using only its own crew. By 1941 this gun was inadequate to deal with the heaviest armoured of Soviet and British tanks. Its replacement, the 5 cm Pak 38 offered better performance (though still only marginal against the new threat) but at 1,000 kg. was at the absolute limit of what the gun's own crew could move into and out of a firing position effectively by hand. The next gun, the 7.5 cm Pak 40 was a very effective tank-killer but at 1,425 kg. was no longer suitable for use by the infantry. A much larger crew and a vehicle was required to move this gun any distance at all and often just to displace it out of its firing position. Many were lost intact simply because they were overrun before their crews could move them. As the guns got bigger to deal with the latest tank technology and became too heavy for tactical employment they also became more expensive. The PAK 36 cost RM 5,730 and 900 work-hours while a PAK 40 cost RM 12,000 and took 2,000 work-hours to build. The situation was so bad that by May 1944 the 14th (Panzerjager) Kompanie of infantry regiments were having their heavy anti-tank guns removed and replaced by the Panzerschreck

Panzerschreck

Panzerschreck was the popular name for the Raketenpanzerbüchse , an 88 mm calibre reusable anti-tank rocket launcher developed by Nazi Germany in World War II. Another popular nickname was Ofenrohr ....

rocket launcher. But with an effective range of only 150 meters this weapon did not provide the depth of fire required for anti-tank defense of the regiment. The only other alternative for a light anti-tank gun had been recoilless weapons, but the German Army was less than enthusiastic because this type of weapons has many shortcomings, particularly a high demand for propellant.

Design and development

In 1943 a specification was issued for a lightweight anti-tank gun that used less propellant than a rocket or recoilless weapon yet was sufficiently accurate to hit a 1-meter square target at 750 meters range. Rheinmetall-Borsig proposed a design to meet this requirement using the new high-low pressure ballistic principle, also known as the Hoch-Niederdruck system. In this system high pressure caused by the combustion of the propellant was confined to the breech section, which was relatively heavy, and did not act directly on the projectile. It was allowed to bleed gradually into the barrel at a controlled rate and lower pressure to propel the projectile. Thus the barrel could be exceptionally light in a weapon that still had the advantages which accrue from high pressure. The carriage too could be very light although initial prototypes carriages proved to be too light and had to be redesigned. The resulting PAW 600 (later redesignated 8H63) gun weighed about 600 kg, less than half that of the 7,5cm Pak 40 while having comparable armor penetration out to its full effective anti-tank range of 750 meters.

Unlike previous anti-tank guns which relied on firing steel projectiles at high velocities to penetrate heavy armor, the 8H63 was designed to fire shaped charge

Shaped charge

A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...

 ammunition (called also hollow-charge ammunition, high explosive anti-tank, or HEAT). Because shaped charge warheads perform best when no spin is imparted on the projectile the 8H63 was a smoothbore

Smoothbore

A smoothbore weapon is one which has a barrel without rifling. Smoothbores range from handheld firearms to powerful tank guns and large artillery mortars.-History of firearms and rifling:...

 design. To simplify development and manufacture the projectiles used were based on the widely used 8 cm Granatwerfer 34 mortar (actual caliber 81.4 mm). This allowed the use of existing tooling in the manufacture of ammunition, which reduced cost. The cartridge case was developed from the 10.5 cm leFH 18

10.5 cm leFH 18

-History:The 10.5 cm leFH 18 was the standard divisional field howitzer used by the Wehrmacht during the Second World War. It was designed and developed by Rheinmetall in 1929-30 and entered service with the Wehrmacht in 1935. Generally it did not equip independent artillery battalions until...

 howitzer.

The standard shaped charge projectile designated 8 cm W Gr Patr H1 4462 weighed 2.70 kg. The propelling charge was 360 gm of Digl B1 P (compared to a 3.8 kg propelling charge in a PAK 40) and with a muzzle velocity of 520 mps this had an effective range of 750 meters against a tank-sized target. Armor penetration was 140mm of vertical armor which was comparable to the 7.5 cm PAK 40 firing the rare and expensive tungsten-cored AP40 shot.

Other uses and rounds

Because the ammunition was developed from the standard infantry mortar any type of round developed for the mortar could have been readily adapted for the 8H63 including high-explosive (HE) round, smoke round, and illuminating round. HE round, the 8 cm W Gr Patr 5071 with a 4.46 kg projectile and total round weight of 8.30 kg was developed. This could employ 3 different charge increments for maximum ranges of 3,400 meters @ 220 mps, 5,600 meters @ 320 mps or 6,200 meters at 420 mps - about 3 times farther than the mortar and with the possibility of direct or indirect fire. This performance brings up another interesting feature of this gun. Traditional high-velocity anti-tank guns were very inefficient when employed as field artillery firing explosive rounds in support of the infantry. The thick projectile walls necessary to withstand high velocities ensured a small explosive payload and the amount of propellent used was wasteful. The guns also fired at low trajectories (+22 degrees for a PAK 40) which limited their utility. For this reason the German Army had always employed Infantry Guns such as the 7.5 cm leichtes Infanteriegeschütz 18

7.5 cm leichtes Infanteriegeschütz 18

The 7.5 cm leichtes Infanteriegeschütz 18 was an infantry support gun of the German Wehrmacht used during World War II.- History :...

 at the regimental level to provide fire support under the direct and immediate control of the infantry. This meant every infantry regiment had an infantry gun kompanie for use against unarmored targets and a tank destroyer (anti-tank gun) company for use against armored targets. The 8H63, firing an explosive round had lethality comparable to if not superior to the 7.5 cm infantry gun and much greater range. The 8H63's multi-charge cartridge and +32 degree elevation could have allowed the merger of the infantry and anti-tank gun categories with a resulting savings in production, logistics, and precious manpower. The 8H63 was to be organized under the new 1945 Table of Organization and Equipment (TO&E) in anti-tank companies of 12 guns with 104 men, replacing the anti-tank and infantry gun companies (300+ men) of previous organizations.

Production

Some 260 guns and 34,800 rounds of ammunition were completed from December 1944 with 81 guns delivered to the troops in January 1945 and 155 listed on March 1, 1945. Plans had called for the production of 1,000 guns per 4,000,000 anti-tank and 800,000 explosive shells per month. Production models had either the purpose-built light carriage or used redundant PAK 38 carriages and PAK 40 muzzle brakes and were slightly heavier.

Further development perspectives

Several self-propelled models were proposed in 1945 but the war ended before even prototypes could be built. It is clear that had the war in Europe carried on longer the 8H63 would have been a major factor and would likely have replaced the towed PAK 40 and various 7.5 cm infantry guns in production.

Krupp

Krupp

The Krupp family , a prominent 400-year-old German dynasty from Essen, have become famous for their steel production and for their manufacture of ammunition and armaments. The family business, known as Friedrich Krupp AG Hoesch-Krupp, was the largest company in Europe at the beginning of the 20th...

 was also developing an enlarged 10 cm design known as the 10 cm PAW 1000 or 10H64

10H64

The 10 cm PAW 600 - later re-designated 10H64 - was a lightweight anti-tank gun that utilized a high-low pressure system to fire hollow charge warheads .-Background:...

 at the end of the war but none reached production. This would have had an armor penetration increased to 200 mm in a gun of about 1,000 kg with the effective range against tanks increased to 1,000 meters.

Nomenclature

The Panzerabwehrwerfer 600 ("anti-tank thrower") designation was used by Rheinmetall during the design phase. The service designation was 8H63 in accordance to the new designation system used during the last year of the war.
In 1944-5 the Germans changed their system of artillery designations from the old "year" system. Each weapon was to have a number showing their caliber group, a letter denoting ammunition group, and the last two digits were from the weapon drawing number. In this case 8 denoted 81.4 mm caliber using the H group of ammunition. The shells were all to be designated as H with a 4 digit number, the first three were the drawing number and the last was the shell's category from the following list:

#	Shell type	#	Shell type
1	high explosive	5	gas
2	hollow charge anti-tank	7	incendiary
3	armor-piercing	8	leaflet
4	high explosive, high capacity	9	practice
5	smoke	10	proof projectile