Wz. 35 anti-tank rifle

Karabin przeciwpancerny wzór 35 (abbreviated "kb ppanc wz. 35"; "anti-tank rifle, model 35"), also Uruguay, was a Polish 7.9 mm anti-tank rifle used by the Polish Army during the Invasion of Poland of 1939. It was also known by its codename Uruguay (kb Urugwaj) (kb Ur), or by the name of its designer, Józef Maroszek.

Secrecy and confusion
The weapon was initially a top secret of the Polish Army, and was also known by various codenames. Until mobilization in 1939, the combat-ready rifles were held in closed crates enigmatically marked: "Do not open! Surveillance equipment!"

One of the rifle's cover names was Uruguay (Polish: Urugwaj, hence Ur), the country to which the "surveillance equipment" was supposedly being exported.

After the fall of Poland, the German army captured large numbers of the kb ppanc wz.35 and used it as "Panzerbüchse 35 (polnisch)" (abbreviated "PzB 35(p)"). The Italian army also benefited from the booty and used it under its own designation as "fucile controcarro 35(P)." Both names translate roughly as "Anti-tank Rifle 35 (Polish)."

In early 1940, one of the rifles, its stock and barrel sawed off, was smuggled out of Poland across the Tatra Mountains into Hungary for the Allies by Krystyna Skarbek and Polish fellow couriers. The rifle never saw service with the Allies, however, because the drawings and specifications had been destroyed by the Poles during the invasion of Poland; reverse engineering would have required too much time.

Description
In appearance it resembled a rifle with a longer-than-normal barrel supported by a bipod at the front of the wooden stock. It was a bolt-action rifle, fed from a 4-round box magazine. The barrel was equipped with a muzzle brake to limit the recoil. The brake absorbed approximately 65% of the shot energy and the recoil was comparable to the standard Mauser rifle, even though the cartridge carried more than twice the amount of propellant. It had fitted iron sights fixed for a 300-meter range.

Unlike other anti-material rifles of the time, the wz. 35 did not use an armour-piercing bullet with a hard core, but rather a lead core, full metal jacket bullet weighing 14.579 g; due to the high muzzle velocity this was effective even under shallow angles, as instead of ricocheting, the bullet would "stick" to the armour and punch a roughly 20 mm diameter hole. Calculated kinetic energy, by shot, before brake was about 11,850 J. The high energy was due to the relatively long barrel, and nitro powder giving a muzzle velocity of 1,275 m/s.

Ammunition


In the late 1920s the Polish General Staff started the development of a light anti-tank weapon for the Polish infantry. In 1931 Lt. Colonel Tadeusz Felsztyn from the Institute of Armament Technology in Warsaw started the first tests of various low-calibre cartridges. After the tests of German-made Hagler bullets proved the possibilities of that type ammunition in perforating steel plate, the National Ammunition Factory in Skarżysko-Kamienna was ordered to develop its own 7.92 mm cartridge with a muzzle velocity of over 1,000 meters per second. After a series of tests, the new DS cartridge was proposed. Visit for a picture of the ammunition.

The DS ammunition was based on a standard 7.9 mm bullet as used by both the Mauser rifle Model 1898 (wz.98) and its Polish variant the Karabinek wz.29. The length of the cartridge was extended to 131.2 mm and the overall weight was 64.25 g. After an additional series of tests the copper cartridge case was replaced with a case made of brass (67% copper/ 23% zinc).

Uniquely, compared to other armour-piercing designs, the DS round instead of using tungsten or a similar hard metal for the core had lead, as with standard ball, but with a steel jacket. The penetration was not through punching the core through the armor but from the impact of the bullet flattening against the plate, transferring kinetic energy to the metal. The key to success for this technique was a very high bullet velocity. The result was that the bullet was punching a spall, about 20 mm in diameter, out of the armour, a size larger than the actual rifle caliber. The fragment would then ricochet inside of an armoured vehicle, possibly damaging the engine or killing the crew (an effect similar to that of a modern HESH tank round).

Rifle
Simultaneous to the development of the ammunition, a young graduate of the Warsaw University of Technology, Józef Maroszek was ordered to design an anti-tank rifle. On August 1, 1935, the Committee of Equipment and Armament officially ordered the rifle and in October the first tests of the new weapon started.

The rifle was based on the Karabiner 98k, with the action modified to sustain the higher pressure of the new cartridge and the barrel lengthened significantly. The first tests carried out in Brześć and Pionki showed that the new weapon was capable of penetrating a 15 mm steel plate at a distance of 300 metres with similar results against angled steel plate. Initially the barrel could only sustain up to 30 shots, after which it had to be replaced with a new one. However, this drawback was soon corrected and the final prototype could fire approximately 300 shots. The committee accepted the new design on November 25, 1935, and in December the Ministry of Military Affairs ordered the delivery of 5 rifles, 5000 cartridges and a set of spare barrels for further tests.

After the tests carried out by the Centre of Infantry Training in Rembertów proved the effectiveness and reliability of kbk ppanc wz.35, the Ministry ordered 7610 rifles to be delivered to the Polish Army by the end of 1939. It is uncertain how many rifles were actually produced, but it is often estimated that there were more than 6,500 delivered by September 1939.

Use
The rifle was the main anti-tank weapon of an infantry platoon. Each infantry company and cavalry squadron was to be equipped with three rifles, each operated by a team of two soldiers. Additional anti-tank teams were to be created at a later stage. Although the weapon was successively introduced to the units, it remained a top secret. The rifles were kept in closed wooden crates, each marked with a number and a notice do not open; surveillance equipment. The teams were trained in secret military facilities just before the war, beginning in July 1939, and had to swear to preserve the secret.

The rifle was carried by the leader of the two-man rifle team on a carrying strap. The other member of the squad was his aide and provided him with cover while he was reloading. The weapon was usually fired from prone supported position with the bipod attached to the barrel. However, it could be also used in other positions, like prone unsupported and crouch. The effective range was 300 metres and the weapon was effective against all German tanks of the period (the Panzer I, II and III, as well as the Czech-made LT-35 and LT-38) at 100 meters. At up to 400 meters it could penetrate all lightly armored vehicles. It could penetrate 15 mm of armor, sloped at 30° at 300 m distance, or 33 mm of armor at 100 m. Interestingly, an Italian manual stated maximum penetration as 40 mm.

Panzerbüchse 35(p)
Despite well-established opinion, the Karabin przeciwpancerny wz.35 was extensively used during the Invasion of Poland of 1939 by most Polish units. After Poland was overrun by Germany and the Soviet Union, large quantities of this weapon were captured. The Germans pressed it into service as Panzerbüchse 35 (polnisch) (PzB 35(p)), and sped up work on their own simplified, one-shot anti-tank rifle Panzerbüchse 39 (PzB 39). According to some sources, however, the Germans replaced the DS bullets in the captured ammunition with their own 7.92 mm hardened-steel-core bullets from the PzB 39.

Also, several features of the Polish rifle, most notably the lock, were used in developing the Soviet PTRD, 14.5 mm anti-tank rifle.

In 1940, Germany sold some 800 Polish antitank rifles to the Italian armed forces, which used them in combat until the end of World War II.

Survivors
The number of surviving .wz 35 rifles is unclear; it has often been claimed that only four specimens survive, which were exported to the United States in the 1950s. However, there are at least two more in the United Kingdom. One is on exhibit in Poland, at Warsaw's Polish Army Museum; another is located in Armament Museum in Poznań Citadel.

The .wz 35 has recently been appraised in England at $130,000.