The Premiers is what I've run in 20 cal and shot several squirrels dead, at around 680 mv.......and out to a good distance, 50-70 yds...
RWS guns sometimes prefer RWS pellets like the Roundnose dome and the pointed ones. Bore size varies in airguns, and pellets vary as well.
I think you will find that gun deadly on squirrels
Interesting, both RWS hollow points and field points came with the rifle package but I shot them all before getting to hunt with it. Might need to order some more. Thanks!