Pressure chamber: 1 foot of 3/4'' galvanized steel pipe
valve: 1/2'' ballvalve
Barrel: 60cm of 1/2'' poly pipe
I don't know what pressure i pump it up to but im guessing maybe 65 to 80psi...
I used to have 1/2'' gavenized steel barrel and it was really rough and crap.....but when I got some pipe 1/2 poly pipe for my future piston gun, I was shocked to fined out that 1/2'' threads go into a 1/2'' ballvalve

batterys fit perfect...good barrel=good performance

yesterday I helped my friend make one pretty much exactly the same but i think he put a wire stock on it.....he should be posting it soon