Does anyone have any experience with one of these kits a a RWS Diana 350 magnum rifle did it calm the recoil without losing power ?
I agree. I have the Diana 34 and am getting around 680fps using JSB 15.89gr pellets and my gun has the Vortek spring."JohnL57"
Having said that your numbers may be a little slow for a 350-I'd expect something like that from the milder model 34.