The Czech-made ZK-383 submachine gun is a bit of an oddball in the world of submachine guns. It has several design features typically associated with rifle-caliber light machine guns - an integral bipod and a quick-change barrel. In fact, the ZK-383 was designed to be a hybrid gun, usable as either a standard SMG or in a support role off the bipod.
Another interesting mechanical feature of the ZK-383 is the removable weight in its bolt, which allows the shooter to choose between fast and slow rates of fire by removing the weight or leaving it in place. In my shooting, the slow rate was about 470 rpm and the fast rate was about 750 rpm. Personally, I preferred the slow rate - but both were exceedingly easy to control. The gun is fantastically well made, as one might expect from a pre-war Czech weapon.
This particular ZK-383 is an original transferrable C&R gun, brought back to the US by a veteran after WWII. It is a very early production gun, with a German-marked magazine well but no other German markings, and clearly did not see much abuse during the war.
In all honesty, this is the overall best military submachine gun I think I have ever fired.