I'd definitely test them. There may be not rationale that they might not function just fine in your Beeman. I've experienced great luck with RWS pellets in all of my airguns (Hatsan, Crossman, Benjamin and so on.). I'd try out a tin and see how your Grizzly likes them as https://super17768999.shoutmyblog.com/35079806/the-fact-about-super177-that-no-one-is-suggesting