I'd definitely test them. There is not explanation that they'd not get the job done just fantastic with your Beeman. I've had very good luck with RWS pellets in all of my airguns (Hatsan, Crossman, Benjamin and so on.). I'd personally check out a tin and see how your Grizzly https://arthurkwhsd.idblogmaker.com/35056820/facts-about-super177-revealed