ramses wrote:What I don't like about that design is that if you fire the gun upside down (could happen), you shoot off the end of your barrel.
Even if you point it at a slight downward angle as I mentioned.
Also, they vent combustion gas right back at the operator
True, though given the small bore of the vents it would probably not be that much of an issue.
Anyway, decided to give this another go. My previous efforts floundered because I made them too weak, and because I only had airsoft BBs which were just 0.5mm greater in diameter that the 0.22" pellets I was using.
This time round, I used the aluminium tube and hammer-fit epoxied delrin endcap construction that has served me well with high mix hybrids. I also have a selection of plastic bead sizes (7.59mm, 7.88mm and 8.10mm) to choose a blocker from. The centre bore should allow the barrel gasses to leak out, though if that's still too loud I'll block it up. Blowing through the thing easily lifts the beads to block the muzzle, my fear again is that it will strike the pellet on the way up.
I put a female 1/2" UNF thread on the back to be able to attach it to my Daystate for testing, now that it's in my commercial interest to make a compact and effective airgun silencer
watch this space.