ZB vz. 30

The ZB-30 and ZB-30J were Czechoslovakian light machine guns that saw extensive use during World War II.
History.
The Zb 30 and Zb 30J were the later versions of the famous Czechoslovak machine gun, the ZB-26. However, the ZB-30 had some design differences, making it similar to the later ZGB-33, which was an early prototype of the Bren gun. Like the ZB-26, the "Wehrmacht" adopted the ZB-30 after the occupation of Czechoslovakia, renaming it the MG30(t); it was used in the same role as the MG34, as a light machine gun. In the opening phases of World War II, the ZB-30 in 7.92 mm Mauser caliber was used in large numbers by elements of the German "Waffen-SS", who did not initially have full access to standard "Wehrmacht" supply channels.
Comparison of original ZB vz.26 and modifications:
Note - The ZB 30J was a late design iteration of the ZB 30 for sale to Yugoslavia (originally spelled with a J) that featured an adjustable gas system so commonly available light and heavy 7.92mm ball ammunition would cycle the mechanism.