the fittings are all PN18 and the pipe is PN12 (approx. 174psi), both 40 and 50mm (im in Australia). the barrel (removable) and chamber are both 1m long (although the barrel has a fair bit of dead space)
the valve was fairly difficult, as i had to sand the T to fit the 50mm pipe the whole way through. it took a while but with a dremel i eventually got the pipe to fit.
the piston is made from a 6mm bolt and a nut, two circular cut-outs of 6mm ply, 2 large washers (ends of the piston), 6 washers for spacers between the ply and other washers, a bit of aluminium tubing and 6 orings. i used 6 orings, ranging from fairly small to the ones visible to help stop them slipping out as it goes past the valve opening.
my first shot with it was at 30psi, the golf ball flew out the barrel and hit a tree about 20m away, broke a branch and ricocheted over into the paddock, about 50-60m.
that surprised me as how well it actually shot.2nd shot was at 30psi... and the golf ball flew!!!
it went about as far as i can hit one with a club, and thats about 200m (ok, it probablyonly went about 100-130ish 
). i was only using this by pulling the piston out the back of the valve by hand, as i am having a few issues with the orings catching on the valve opening. eventually it will have a bumper and bolt to reload, and use a spring to pull the valve back, so it will have an actual trigger.i cant wait to finish the bumper and trigger so i can actually try this thing at higher pressures!!!
sorry if that was a bit long and ask away with any questions you have,
tom
