It isn't just the steel it's also the locking system.The Marlin will take pressures of 40,000 psi but I wouldn't want to go above 28,000 for the RB, that's the SAAMI limit for the cartridge.Considering the performance of the typical factory loads which are loaded to only about 18,000 the cartridge loaded to 28,000 is very potent.Are you going after T-Rex ?