I owned a Hatsan several years ago. I didn't care for the rifle and have no idea what happened to it. It looks like that .25 is doing the job for you and if you like it, more power to you. That .25 cal pellet just smacks them down, doesn't it? My little BSA shoots H&N FTT @ only 600 fps but when one hits a squirrel they just drop, if I did my part.
Good kills, good work.