The Poles were not wholly ill-equipped during the German invasion of September 1939. Its tank-stopping capabilities were reinforced by the introduction of the KB wz. 35 rifle, a heavy-caliber anti-tank solution that was produced in 3,500 examples. However, most ended up seeing combat service in enemy hands than in defense of the homeland and the caliber and its associated rifle design eventually fell to firearms history amidst the growing strength of enemy armor protection.
The KB wz. 35 rifle series had its origins in pre-war Poland and developed around the 7.92x107mm DS lead core cartridge. The cartridge itself was Polish in origin, developed by one Lieutenant Colonel Tadeusz Felsztyn specifically for the anti-armor / anti-tank role and the rifle design followed it. The cartridge was based on the German 7.92x57mm Mauser round and the finalized wz. 35 rifle indeed mimicked the Mauser M1918 "T-Gewehr" AT rifle in both form and function, the German version debuted during the fighting of World War 1 (1914-1918).
The T-Gewehr became the world's first dedicated anti-tank rifle design and is detailed elsewhere on this site.
The Polish version featured a loaded weight of 22 pounds with a length reaching 1,760mm while utilizing a 1,200mm long barrel assembly. The wooden stock incorporated the grip handle and shoulder support as well as the forend, the latter completed with an upper section seated over the base of the barrel. The barrel remained exposed along most of its length. The critical metal components were inlaid in the wooden body with the tripped slung under, just aft of the magazine well. A folding bipod sat ahead of the forend in supporting the rifle when firing. A 90-degree bolt handle hung over the right side of the receiver and was capped by a knob for better gripping. The weapon was fed by a four-round detachable box magazine.
Due to the secrecy involved in the rifle's development, the gun was initially housed in crates labeled as "surveillance equipment" with intended "export" to customer Uruguay. As such, the rifles were sometimes referred by the name of "Uruguay" or, alternatively, carried the name of chief designer Jozef Marosek and were therefore recognized as "Marosczek" rifles as well. Manufacture stemmed from Panstwowa Fabryka Karabinow, a sister establishment to the famous Lucznik Arms Factory in Poland.
In practice, the weapon gave good service - a rate-of-fire of up to ten rounds per minute could be reached and muzzle velocity was 4,180 feet per second. Penetration against early-war tanks (Panzer I through Panzer III) was good considering their lighter armor coverage and the rifles were pressed into service from 1939 onwards and issued to two-member rifle teams. Drawbacks included excessive weight and long length which weighed the operator down on marches or when relocating to a more advantageous position on the battlefield. If laying in ambush, the operator held a good chance to surprise an enemy tank and disable some portion of its design - track links, track rollers, engine components and the like.
With the fall of Warsaw and the defeat of the Polish Army by the Axis powers (ultimately to be joined by the Soviet Union in the East), remaining wz. 35 gun stocks fell to the Germans. Any engineering plans regarding this weapon were then destroyed by the retreating Poles lest they fell into enemy hands. In the German inventory the rifle was redesignated to Panzerbuchse 35 (polnisch) - abbreviated to PzB 35(p) - while those passed on to the allied Italians (about 800 examples) became known as Fucile Controcarro 35(p), the "p" simply signifying their Polish design origins.
KB wz.35 rifles were in service until the end of the war in 1945.