NOT KNOWN DETAILS ABOUT SUPER177

I might absolutely test them. There is certainly not rationale that they would not function just fantastic with your Beeman. I've experienced superior luck with RWS pellets in all of my airguns (Hatsan, Crossman, Benjamin etc.). I'd test a tin and find out how your Grizzly likes them as all guns seem to have their favored pellets.The RWS Superdome