I should really cut my losses and stop now....
My "final" setup is:
- 2.74mm spacer threaded onto the rod...pushing the floating valve up further ahead....
-- it was fairly reliable at shooting just below 350fps w/0.20g BBs, but the first couple of shots from a fresh gassing were over.
- I cut the stock barrel back to CQBR length (it extends about 3-5mm past the threading of the outer barrel with the M4A1 extension removed
- Freshly gassed the first shots come out at 340fps...the rest hover in the mid 330 range...last couple are 300-310-ish. I'll have to do some more careful testing.
- With a Madbull Firepig "amplifier" on it....it'll leave a ringing in your ear when shooting in a small workshop....fracken LOUD!
-- best to space the Firepig out if you have a bayonet lug...an o-ring and a nice flashhider collar work perfectly.
NOTE: Whoever decided to start the outer barrel section/threading at 10" instead of 10.5" should be shot...or at least teabagged while he sleeps....
I need a bigger lathe..... (or at least one with a bigger diameter through spindle).