OK guys - rap4 METS yellow dot. BB conversion kit, BB shells
load shell with BB, fill mag then put in gun. Pull trigger, and all I can hear is gas coming through, BB does not move and shell is not ejected. Pull trigger again immediately and everything is OK and works as it should. Pull trigger again and 2 or 3 shells are ejected at once. Pull trigger again, shell jams. Each full mag is usually a combination of the above
solutions I have tried:
adjusting barrel so it doesn't "clamp" the shell
different shells each time, with much the same results
different gas tubes
replaced all core o-rings
tried different mags
adjusted velocity/rof with pressure gauge
replaced kicker spring
checked ejector unit opposite of kicker arm for burrs (results of dry firing)
all problems occur during semi auto fire only, full auto is NOT allowed here in UK.
and that's it - is there anything I have missed?