Light machine gun ZB 30J

The light machine gun ZB 30J, also referred to as vz. 30/37, of the Czechoslovak Arms Factory Brno was a continuation of the successful design of the vz. 26 machine gun.

In the second half of the 1930s, the Czechoslovak Ordnance Factory tried to succeed in the competition for the Yugoslav machine gun market. The first interest of Zbrojovka with the vz. 26 light machine gun was thwarted by strong foreign competition. This was due to the lower unit price and the cheaper establishment of a new armoury in Kragujevac by the competitors, and so Zbrojovka had to go significantly down in price. During later tests of the vz. 30 and vz. 34 machine guns, the characteristics of the different ammunition became unpleasantly apparent, and the elimination of the defects required reconstruction. Also, the customer required certain modifications. And it was these reconstructions that gave rise to another type of the ZB series - the ZB 30J machine gun for Yugoslavia, which was insensitive to the vagaries of ammunition. The ZB 30 J could use the ZB 206 tripod, on which it could partially perform heavy machine gun tasks. The tripod could also be converted to an anti-aircraft firing position. The contract for 15,000 machine guns concluded in July 1936 was later rightly described as a deal only in quotation marks (by the Czechoslovak military attaché in Yugoslavia). Not only did Zbrojovka have to supply a third of the 15,000 units in exchange for the previously delivered vz. 26 machine guns, but the price was also a loss for the manufacturer and the deal was made especially to maintain prestige and preserve the market. After the first part of the contract was fulfilled, production in Brno, further machine guns were then built under licence in Yugoslavia at the armoury in Kragujevac. The Yugoslav army introduced the weapon in 1937 as a standard light machine gun with the designation Puska-Mitralez M.37.

Other countries to which the ZB 30J was sold included Bolivia, Afghanistan and Venezuela. It was also used by the German armed forces (designated 7.92mm LeMG 148(j)), especially by Waffen SS units operating in Yugoslavia. On the other hand, in the ranks of the Yugoslav partisans, machine guns were also found in abundance. The development of the machine guns shows a retreat from the rifling of the barrel (full rifled barrel of the LK vz. 26, smooth barrel of the BREN machine gun). Originally, it was assumed that the rifling would increase the cooling area. In practice, especially in fortifications, ribbing has been shown to be more effective in cooling when the weapon is in motion. If the machine gun was not in motion for an extended period of time while firing, it heated up more quickly because a thermal "cushion" was created around the ribs. The same can be seen for the heavy machine gun vz.37 with the so-called heavy barrel "O".