Thanks Matt! But I'm just the dude paying for it. Jason deserves all the credit possible. He is a master worker on these things!
Did I read that right? Imagine what you could do, power wise, on a 78 with your nifty valve mod!
Looking for more energy, I pulled the valve and proceeded to cut away the entire front (aluminum) part of the valve. I kept only a small ring to retain the -113 valve O-ring. I failed to take photos so here is a sketch:Then I cut a couple of notches into it so I could reach down into the air tube and turn the ring to put a squeeze on the O-ring to help it seal.I then took the conical valve spring and stretched it slightly so it would be long enough to rest against the tank block. The nice thing about the wide base of the conical spring is that it is large enough to straddle the hole bored in the tank block.Got the rifle reassembled and started pumping. No leaks! A victory in and of itself. With it pumped up a little over 2000psi, above the 1550psi regulator setpoint and enough to get a few shots, here's what we have:27.1fpe with Crosman Premier hollow points29.9fpe with JSB 18.13gr heavies:31.3fpe with Kodaik 21.14gr:And lastly, 34.0fpe with Eunjin 28.5gr:That should do it for the energy goals.Next up is to fine-tune the RVA and begin pellet testing and accurizing. It may be the weekend before I post an update on that.
Ron, I can answer the question about 79 vs 78. The initial plan was a 78 Deluxe but at the time we started the project, it was not in stock in .22 cal. So Chris and I talked and I agreed to tune a 79 carefully and see if the results were to his liking, and if not I'd transplant all the go-faster parts to a 78 tube. Chris had already started looking at fitting the 79 to a target stock. With the numbers it is producing, I think we are going to stick with it.Chris, feel free to add or correct.
BRAVO Jason ! I can practically hear Chris just giggling his head off from 2 states away ;-) Hehe,... Here's a little teaser,... We will soon be finding this out ;-)and yeah,... that sound you can hear is me giggling too
Im new to modding and wondering if you could explain the reason for reducing the valve body? Im guessing this has been covered elsewhere, so feel free to tell me to look but any direction is greatly appreciated!
Quote from: Prouzy on March 25, 2015, 01:17:12 PMIm new to modding and wondering if you could explain the reason for reducing the valve body? Im guessing this has been covered elsewhere, so feel free to tell me to look but any direction is greatly appreciated!Hi Chris,It's pretty much all about increasing the volume of regulated air available. In a QB79, normally this volume is pretty much that of the interior of the valve itself...there isn't really an air tube to speak of.As soon as the valve opens and air rushes into the barrel to expel the pellet, the pressure inside the valve (and air tube) falls. The larger the volume of air, the less the pressure falls, thus the higher the average pressure during the shot cycle, giving the pellet a higher velocity / energy.
So the volume of air(flow) following hammer strike/valve opening is NOT limited to the volume in the valve, that makes a whole lot more sense seeing the slots milled into the body :-)