The Krummlauf (English: "curved barrel") is a bent barrel attachment for the Sturmgewehr 44 (StG 44) rifle developed by Germany in World War II. The curved barrel included a periscope sighting device for shooting around corners from a safe position.
It was produced in several variants: an "I" version for infantry use, a "P" version for use in tanks (to cover the dead areas in the close range around the tank and defend against assaulting infantry), versions with 30ð, 45ð, 60ð and 90ð bends, a version for the StG 44 and one for the MG 42. Only the 30ð "I" version for the StG 44 was produced in many numbers.
The bent barrel attachments had very short lifespansâÂÂapproximately 300 rounds for the 30ð version, and 160 rounds for the 45ð variantâÂÂas the barrel and bullets fired were put under great stress. Another problem besides the short life-span was that the bending caused the bullets to shatter and exit the barrel in multiple fragments, producing an unintended shotgun effect. As a result, weapons designers experimented with small vent holes drilled into the Krummlaufs barrel in order to reduce pressure and recoil, allowing the discharged bullets' built-up gases to be released to slow the bullet's velocity as it turned to exit the barrel. Nevertheless, the Krummlaufs lifespan remained the same. A triangular shield was also added to prevent venting gasses from clouding the mirror and optics.
The 30ð model was able to achieve a 35ÃÂ35 cm grouping at 100 m.
The Krummlauf in a Maschinenpistole Vorsatz (P) mount was developed as an alternative close defence weapon for tank destroyers. This mount was fitted to a roof hatch in many Panzer IV/70 (A) vehicles. The tank crew could then attach a StG 44 and use this as a close defence machine gun.
Experiments to adapt the Krummlauf to the PPSh-41 were conducted by the Soviet Union.