Bit of a query here guys , I'm getting a couple of RB moulds made up , one for my 12bore & one for a project 8bore , what is the normal or preferred amount over the groove size , I have read from .002 to .005 , just thought I would check with the guys in the know ?

I don't have the 12 bore measurements to check , but from my records it was .734 , I had a mould made at .737 which throws a .736 ball in WW & that ball only just gets marked by the rifling (semi invisible rifling , sort of) when pushed through the barrels , so I want a larger ball .

8 Bore is .830 Bore & .845 Groove , a plastic Winchester industrial shell can take up to .850 ball with out stretching/bugling the case & is still within chamber specs .

Any opinions would help ?