recently purchased license for Browning Automatic Rifle (via Colt's agent, Belgian company Fabrique Nationale de Herstal) was faulty, and deliveries were delayed, which discouraged the Polish from further orders abroad. Because of that, the Polish ministry decided to order the preparation of a local version of the Browning M1917 at Fabryka Karabinow ("Rifle Factory") in Warsaw. Modifications In mid-1930 the first test models were ready and were sent to various testing ranges. In March 1931 the first 200 models were sent to front-line units for further tests under the designation of Ckm wz.30. Serial production started by the end of that year. Among the most notable differences between the original and the Polish clone were: Different calibre, adapted to the Polish standard 7.92×57mm Mauser ammunition Loophole iron sights replaced with V-notch sights Butt handle of the weapon was lengthened for easier carriage Longer barrel for greater precision and accuracy Rifle lock was modified for easier exchange of used-up barrels The lock was modified for easier handling New mounting was adapted, with a mast for anti-aircraft fire Sights were adapted for anti-aircraft fire as well as a handle for aiming in the air was added Added flame suppressor Three types of a tripod mounting were developed and used in Poland. First was wz.30 mounting for infantry (weight 29.3 kg), superseded with improved wz.34 mounting (26.3 kg). Cavalry adopted more modern wz.36 mounting instead (17 kg). All tripods could be used for anti-aircraft fire, using a mast, transported in a rear leg in case of infantry mountings, or folded below the barrel and fulfilling also a role of a recoil shock absorber, in case of the cavalry mounting. Following the first tests, a series of additional modifications was introduced. In 1938 the trigger mechanism was replaced with a completely new, more reliable system. In addition, the lock was replaced for easier handling and keeping the weapon in good condition. The modified design received the designation of ckm wz.30a, though the name was rarely used by the soldiers themselves. The new version was also the basis of a ckm wz.30/39T design, designed for export to Turkey and adapted to Turkish standard 7.65×53mm Argentine ammunition. However, the design was never introduced in large numbers as the Turkish competition was halted after World War II broke out. In the late 30s, Wilniewczyc and Skrzypinski designed experimental barrels with a rifled oval barrel bore ("Lancaster rifling").