DinerKid wrote:and suddenly i am back to the drawing board.
Add flow restriction(slightly opened ballvalve or cheap flow regulator, smaller tubing/pipe) and do it the way I mentioned earlier.
You stated that it worked when you did what jrrdw mentioned...same theory.
What c11man mentioned is worth experimentation..I've lost interest in sprinkler valves myself, (but I might as well get the most from the one's I still have).
Like I said before, about a week ago I used propane (Nothing more than pressure source), with tons of flow restriction, on a 1.5" chamber gun (srry, can't get exact volume now), and it BaWHUMPED fast enough for semi-auto.