Its working well, I shot a few blanks at 100PSI which were very loud (thats always a good sign) and I shot a blank at my curtains which some how brought them and the curtain rail down, revealing a very confused looking air conditioner repair man on the neighbours roof seemingly ducking for cover, I managed to hit the deck and crawl away from the window without him seeing me
The problems I have now are; I need to find a massive washer for the piston cos the pressure keeps bending the sealing face, I put a very thin washer on that was quite big and the pressure folded it in on itself after one shot

Also the sprinkler is leaking quite a bit from the exhaust side of it, maybe the hose clamps or are slowly leaking and making the diaphragm seal leak, I'm not sure, hopefully the seal is just dirty or something.
Ok heres what it looks like so far, haven't done the barrel support yet or painted