I'd personally absolutely test them. There may be not rationale that they might not do the job just fine inside your Beeman. I've had excellent luck with RWS pellets in all of my airguns (Hatsan, Crossman, Benjamin and so forth.). I'd try out a tin and see how your Grizzly likes them as all guns seem to have their favored pellets.Umarex 12 Gram CO2