The Vz. 33 percussion primer is a Skoda design of which there are three sizes, i.e. Vz. 33 dv. (long), Vz. 33 Sv. (medium) and Vz. 33 Kv. (short). These sizes can be identified by the designations stamped in the base of the primers. The long primer differs from the me-dium in the length of the magazine which is 1.97 inches instead of 1.35 inches. Details of the short primer are not yet available.

The primer shown in the drawing is the Vz. 33 dv. with the long magazine. The cap and the percussion arrangement located inside the brass body, are of an unusual design. The copper cap is enlarged in diameter near the mouth to accommodate the brass anvile and contains the initiating composition in the smaller portion at the base. The composition consists of mercury fuliminate 29.9 per cent, potassium chlorate 23.5 per cent, antimony sulphide 35.7 per cent and 10.9 per cent of ground glass. The 0.5 grain pressing of the composition is shaped on the surface to conform with the anvil and is covered by a tinfoil disc without varnish. The anvil consists of a brass circular disc with a central protube-rance underneath and a recess in the top. Four radial slots for the passage of the flash are formed around the protuberance. The cap is held between a brass closing pulg, with a central flash hole, and the percussion arrangement.

The percussion arrangement consists of a steel ball supported in a brass holder by a pla-ted steel disc. The holder is cylindrical with a recess at the top to receive the cap and another at the base into which the disc is sprung. The ball is located in a channel bet-ween the two recesses where it is held between the base of the cap and the spring disc.

When the diaphragm at the base of the primer is forced by the striker of the firing me-chanism, the ball is driven against the base of the cap and crushes the initiating compo-sition on the anvil. The flash passes through the slots in the anvil and through the hole in the closing plug to the powder in the magazine. The use of the ball for transmitting the striker blow to the cap ensures a central blow on the cap even if the striker of the firing mechanism is not concentric.