Cheers for posting again.
I tightened up the knurled part and the 1 grub again. This time I moved the custom wheel inwards and locked it against the inner ring that has the 3 grubs. It's all solid at the moment but only tried a few pellets up the garden.
I'll try it tomorrow ( decent day forecast ).
I'm quite happy now though that if it keeps going I can have a bush made up that will replace the inner ring and the outer knurled part ... so one way or another this will be fixed.
Good luck again with yours.
Last edited by skires; 17th February 2014 at 12:14 PM.