I been seeing brass bore guides on Ebay and think it might be something useful. I got the aluminum range rod from Cabelas and it measures .382 that said 3/8in is .375 and thats the biggest bore guide I have seen . My question is if anyone uses a range rod like mine with a 3/8in guide. .007 aint very much but I imagine it might be enough. I've read of guys making rods with 7/16 hickory for large bore so is there a 7/16 bore guide. Track of the wolf only has 3/8. The rod for my Investarms 50 cal is just under 3/8 like .373, guess its from rubbing or age