The piston seal was in the gun (obviously) so not sure how old it is, I did try fitting a new one but buggered up the dovetail part fixing lug because I didn't use the magic Theoben way of fitting it
, I used a Titan no14 spring which I had to shorten by 3 coils as it was impossible trying to get it in the cylinder without doing myself an injury or risk having it torpedo around the shed
, I used the usual .177 AA domed pellets, the spring guide is a snug fit, not tight that you have to really push it hard to get it on.
Like I said before I didn't really give it that much time as the circlip that holds the rear guide in looks a bit worn and I didn't want to risk breaking it as with most Theoben parts now they are either hard to get or bloody expensive, I could have tried some preload washers and that may have got the power up into the 10ftp area but like you say, I think the seal may need replacing but I don't really want to spend another £30 at the moment on another seal when my next project is waiting to be worked on (infact I've just bought some stuff for it today).
Pete