The URZ AP (Univerzální Ruční Zbraň Automatická Puška, lit. universal handheld weapon) Plamen (Czech: flame), and its variants, the LK (Lehký Kulomet, lit. "light machine gun"), TK (Ťažký Kulomet, lit. "heavy machine gun") and T (Tankový Kulomet, lit. "tank machine gun"), was a prototype Czech modular weapon system.
The AP was an attempt by a team of designers in ZB led by Jiří Čermák to create a modular weapon system. Meant to be an export weapon from the get-go, the system was designed to chamber a "foreign type of ammunition" (in this case being 7.62×51mm NATO).
Heavily advertised by ZB, the system attempted to replace just about every type of weapon currently used on the field such as submachine guns to mounted machine guns with one weapon system; while this system was advertised up until the mid-1970s,  the system achieved no sales and fell into obscurity.
The AP prototype is currently located in the Czech Military History Museum, while the whereabouts of the LK, TK and T prototypes remain unknown.
As mentioned above, the AP was a modular weapon system built around a common receiver. The weapon uses a delayed blowback system somewhat similar to a delayed blowback system designed by Ludwig Vorgrimmler, where the weapon has a two-piece bolt with two rollers on the bolt head. These rollers rotate the bolt head as it rides on inclined surfaces on the bolt carrier body and the barrel extension, which helps to slow down the bolt head's movement when the bolt opens. The weapon's charging handle appears to be a rod above the forearm.
The weapon is select-fire; when firing single shots, the weapon operates from a closed bolt while the weapon operates in open bolt when firing fully-automatically. The weapon feeds from a disintegrating belt in all of its configurations. The AP and LK variants use detachable drum magazines with the belt contained within them, with the internal drum magazines having internal belt feed sprockets; the links are collected within the drum magazine itself. The TK and T variants feed from disintegrating belts just like a normal machine gun.
The weapon also has a grenade launching cup attachment that can be fitted on the front of the muzzle; a special low-capacity box magazine can be used to fire the grenades using blank 7.62mm NATO rounds. The weapon has a rear diopter sight.
The weapon uses 7.62×51mm NATO ammunition. While this may not seem that unusual for most weapons of the time, it certainly was for the Czech as the weapon was created during a time when the Warsaw Pact was in effect. (Czechoslovakia was a member of the Pact)
The weapon had four configurations, all of which were supposed to fill some specific role. All four variants were built on a common receiver.
Medium machine gun configuration.
Coaxial-mounted machine gun configuration meant to be used in tanks.