Dan,

The grooves are nice and shallow - .009. Will be shooting 1" round ball with this gun, which cast around 3.45 oz in pure lead. Done a ton of reading/research and received a tremendous amount of help from people on the web (especially Daryl) since my posting and realize hardened RBs are way to go with this bore size in a ML. Selous, Baker, Forsyth, Greener, Finaughty, GP Sanderson, Swayne, Russell all used hardened RBs with their 4 bores and considered them to be rather effective ;-). As these guys are without doubt the most experienced of the big bore gun users it certainly proves a point. Interesting that most of the breech loaders used RBs as well in 4 bore.

Paul, I had the same questions about ball size/weight too but as Daryl said most "4 bores" shoot projectiles ranging from .935 to .975 (5 bore), despite the fact that 4 bore is correct at 1.052. Ross Seyfried says that 1" + bores are actually very rarely encountered in an article about them. 4 Bore is more of a concept than an actual size it seems.

I'll let you know how it goes when I get the gone. Going to start off slow with charge...