Hi, I have inherited a early hw 45 in .177, it probably dates from the late 80's, it was tuned by venom when they were at trapshot, as far as I can see all they have done is put spring guide to other end. The problem I'm finding is power dropping around 100 fps over 15-20 shots, stripped it and found piston really tight in tube. So put it in lathe took some off piston seal ( standard white one) now it falls under its own weight. Was running nice for a while but now has dropped 100 fps again, does anyone know if the seals get worse with age.