Usually, light gas guns (LGG) are used to accelerate projectiles for experimental study of spacecraft shielding performance under impact of space debris. A projectile is placed into polymeric non-split sabot to provide obturation of gas in the LGG barrel. After exit from the barrel, the sabot or its fragments that fly after the projectile, should be separated (cut-off) or deviated from the projectile flight-line. According to a novel approach, a special guard ring mounted at the barrel muzzle is used for fragmentation of a spherical projectile sabot at exit from the LGG barrel, and thin plastic bonded HE placed at the surface of a bush in the guard-plate is used to cut-off the sabot fragments. This approach was tried by numerical simulation and proved by experimental testing.