Well, meh.

Threading the stem and heads cured aaaall the problems I’ve been having. Breech hardly moves a whisker now and the heads screw off pretty quick so it’s not much of a deal-breaker. The floating heads just wouldn’t work, not even with the breech locked over, still got bounce which caused FPS inconsistencies and deformed the cocking-knob against the frame. Then the dreaded MG-mode returned at lower pressures, though very minor. Never did it with steel heads, so I guess the lower-weight Delrin made a difference there.

The lower max FPS is down to the aperture, I’ve discovered it’s 5mm. I have no idea how that happened, I’d previously tried 5mm and it was too big. I was sure I’d made this one 4mm or 4.5mm, I must have been having a blond moment. Still, I’m getting 1000fps with 30mm of spacers, which is pretty good for these pellets. Got a bunny at 60 yards yesterday, and a very small one at that, straight through the base of the head (all I could see of it, it was behind a five-bar gate).

That tank-ping everyone talks about, it’s caused by the breech hitting the bottle. I’ve cured it on my rig by making the collar so thick (4mm) it can’t bottom-out. Should produce a flatter fps-curve too.

Anyway, rifle is shooting sweet right now. Next valve I’ll try 4mm for the aperture and see how that likes the 3mm seal-rod through it. Hopefully it won’t be too restrictive. 😀