This will fit the magazine on the Hatsan Carnivore, the chamber may or may not require work to allow the bullet to chamber easily…. and will stabilize in the Hatsan barrel…. It fits the .25 cal MRod magazine modified to .30 cal by AirGunLab…. I don’t know if it will stabilize in the 0.300″ cal x 0.294″ land 26″ twist TJ’s barrel that Sean Pero and I designed, likely will if you don’t push it too fast….