NOT KNOWN DETAILS ABOUT SUPER177

I'd personally certainly try out them. There may be not reason that they would not perform just great within your Beeman. I have had very good luck with RWS pellets in all of my airguns (Hatsan, Crossman, Benjamin and many others.). I'd personally try a tin and find out how your Grizzly likes them as all guns appear to have their favorite pellets.T