Originally Posted by
Hsing-ee
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.