Quote Originally Posted by customstocker View Post
the Hungarian built feg gpm has a more complicated but very similar reservoir with the valve contained within . ive just built 2 units ( with the kind help & advice from chris buxton ) that screw onto the giffard thread M20 x 2mm pitch & have a similar internal layout as the giffard has (it was based on the giffard valve ) at the front end is an adapter , slightly off set to allow the connection of an 88 gramme umarex disposable co2 capsule or the 12 gramme adapter that gamo supply . a 12 gramme capsule gives around 35 shots on full power in the 177 calibre version. nice guns these . i would post up pics but have problems using photobucket & hate all the spam reminders that they send me . the giffard was for me such an inspiring air rifle that i used 1 of these hand made valve / reservoir units on a rimfire rifle that i changed to mirror the giffard mechanism , basically to see if it was possible to do , its finished now & is a little lighter than a giffard but gives a similar performance in the 177 calibre . i based all the screw threads on the giffard reciever but used the original rimfire hammer & a valve pin to blow open the valve . having had to make a giffard type mainspring last year with a roller on its tip & 2 holes at its rear end , i was glad to have a working lock to begin this project with ....otherwise its an awful lot of filing .
Of course, I would have no idea about the internal works of a feg gpm. Are there any schematics available showing the cylinder valve?