The invention relates to a training weapon system (1) intended for a recoilless antitank rifle (2), the training weapon system (1) comprising a sub-caliber barrel (3) for firing sub-caliber practice projectiles (4) provided with base plates (5), the sub-caliber barrel (3) being arranged in a shell-like body (6) in the barrel (7) of the recoilless antitank rifle (2), the front part of the sub-caliber barrel (3) being fitted in a guide part (8) for centering the barrel (3), and a rear part of the barrel (3) being fitted in a breech (9), comprising a firing channel (10) and a nozzle screw thread (11) for fitting a nozzle screw (12), which is arranged in the rear part of the shell-like body (6). The invention is characterized in that the training weapon system (1) comprises at least one locking part (13, 14), the function of which is to prevent the nozzle screw (12) or the base plate (5) of the projectile (4) or part of the base plate (5) being expelled backwards through the nozzle funnel (21) of the antitank rif
