I'd absolutely attempt them. There is certainly not explanation that they'd not perform just good in your Beeman. I've experienced fantastic luck with RWS pellets in all of my airguns (Hatsan, Crossman, Benjamin and so on.). I'd personally try out a tin and find out how your Grizzly likes them https://lorenzorguht.ltfblog.com/34833244/not-known-factual-statements-about-super177