I think Bull Shop's 460 grain .504s are a safe bet for most any of the 97s. The .5045 sizing works well in the UMags but also worked well in my (now Woodgoat's) .504 Whitetail. The barrels that are a little undersized are more uncommon - and seem mostly to have been used on the White Lightnings.
Chapman, they'll shoot better... it's just that Dave can't hit chit.
