weird...just plain weird...
Rebuilt the mechbox...new piston, piston head, cylinder head, nozzle...400fps spring, Guarder black hopup rubber/nub, KA hopup unit, different M4 inner...best it'll do is a meager 330fps...
I swapped a complete new upper onto it...systema hopup, 6.01mm 300mm short inner...shot 330-ish...
Tried my upper on another lower (that should shoot 350)...and it shot just under 340fps....
Confused...but resisted the urge to chuck it against the wall...so at least the evening ended ok...
