Quote Originally Posted by Hsing-ee View Post
It should be making a lot more power than a 25mm job if it has a proportionally longer stroke as well as the bore. The 25mm ones are just in the sweet spot for 11-12 fpe. Scirrocos were making 20 fpe on FAC IIRC. Have you tried measuring the transfer port volume by using the shank of drill bit?

Are you saying the piston seals are hard when they are new? It's a shame it is such a b'stard to strip and reassemble, sounds like a nightmare. Would building a better spring compressor help, something with more control like straps or something?

The tuners do seem to like their 'O' rings, but then they have got the gear to true up their cylinders to perfect. I still think parachutes are the best for most guns and most home tunes. The BSA Mercury, Airsporter and Meteor did give excellent consistency when fitted with the 'O' rings, but I think they were robbing power through lost volume and friction.
To be honest Alistair I've not done any measuring as I knew from reading lots of guff that they are a sod to get up to power so just wanted to see if I could get good power out of it before getting to involved, if it had made decent power then I was thinking of getting a lighter piston made up with a OZ piston seal (apparently they do a 27mm parachute seal) but to be honest now I can't be arsed, the strange thing is it even twanged with a tight fitting delrin guide, I just think it's one of those rifles that has just got to be left alone in its original form, I'll get my summer holiday over with and think about getting another new piston seal (I know how to fit them now so hopefully won't bugger it up like the one I just bought) and a pump and return it to it's former glory.

Pete