The fpv's introduced in many armies are intended to protect soldiers in battle from flying fragments. Bullets of twist- stabilized weapons will penetrate fpv's. This test was designed to determine whether the use of fpv's leads to a variation of the wounding capacity of the bullet. It examined the following parameters: stability of bullets (a twist-stabilized bullet is stable if the angle of incidence does not exceed two degrees); change in the sectional area of bullets; energy drop; and the maximum size of the temporary wound cavity. The temporary wound cavity is a short-time phenomenon of shots in tissue. The "narrow channel" is the part of the track of gunshot wounds when the bullet is stable. At the end of the narrow channel, the angle of incidence increases, the effective area of the bullet enlarges, and more energy is transferred to the tissue; this results in an expansion of the temporary wound cavity. Three makes of fpv's commercially available for military use at different prices were tested. Findings show that approximately one-third of all bullets became immediately unstable. This resulted in a shortening of the narrow channel. The diameters of the temporary wound cavities may decrease compared to unprotected persons, but may increase with high-energy bullets. The degree of injuries is thus variable and cannot be predicted generally, but it can be determined empirically for specific bullets as well as for certain types of vests. 5 tables and 8 references