Mike - Thanks for the info
I slugged the bore at .775" with .003/.004" grooves (as good as I could get it)

Twist is approx 1 in 30" ish (as far as I can see)

The only 10 bore cases I have are plastic, but my RB mould .775" fits in both!

I assume to use plastic with Black Powder is a no-no? (it is only BP proofed so would not risk nitro loads in it) Daryl?

I will contact Jeff Tanner (he [the father] made some 8 bore stuff some years ago for me) as proper brass cases the way to go, unless I can get some suitable cardboard ones

Thanks again guys

Tony