It depends on what you mean by a "bulletproof vest." The body armor worn my the military consists of a dual layer of protection. The primary armor is a composite ceramic/Kevlar ballistic SAPI (Small Arms Protection Insert) plate that is rated to stop a 7.62mm rifle round, and is worn in a carrier that contains a ballistic insert that will stop low-velocity handgun rounds. The SAPI plate would stop a knife, or a sword, or a sledgehammer for that matter. The ballistic mat, however, would not. Because of the weight and bulkiness of this dual-layer military system, civilian patrol officers typically do not use the SAPI plates. The "bulletproof" vests they wear generally only contains the mat-type ballistic inserts, since most criminals they might go up against are armed with handguns, not rifles.
U.S. Army Airborne - Combat Infantry - Follow Me!!