Okay guys, tried my marker again this morning... cleaned out the ball detent, tried a different barrel and some new paint
Still had the same problem, I can manually feed balls into the feed neck, cock the gun, then blow down the feed neck, and the ball comes wizzing out no problems, without even needing to gas it up...
Fired it again this morning, all seemed to go well for about 30-40 shots, then wham... was rapid firing and about 5-6 balls got stuck in the breach!! doh
Can't seem to find anything that can be causing the problem
Looks like its off to a techy to look at unless anyone has any more ides??
Cheers
Dave