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(The .30-.338 Keele Mag.) . . is that as simple as you have it typed? Imperial lube some Lapua or WW 300WM cases in a 30-338 FL die? That would be especially nice when the shot count goes up and you can chase the lands out a bit further.
[/ QUOTE ]I think so. Use an expander ball in the full-length die to iron out the dimple ring in the Keele case neck where the original .300 WM shoulder-neck junction was. Don't turn/uniform any necks until after the Keele case has been fired once. That dimple ring doesn't seem to hurt accuracy at all.
When I got my first .30-.338 Keele barrel, I ran 40 new .300 WM cases through my RCBS die, then seated Sierra HPMK 190's in half and 200's in half. Tested 'em at 1000 yards with a few sighters to center up then back to back 15-shot groups with each. Both groups were about 5 inches high and 6 inches wide; didn't correct for any wind. The group of 190's was centered 5 inches above the middle of the group of 200's. New cases are just fine with me......
However, if one plans on lengthening an existing standard .30-.338 chamber, be sure the floating pilot on the necking reamer is a proper tight fit in the rifling and will only lengthen the chamber neck keeping it at the same diameter. This is a tricky process and I'd just as soon have the barrel set back one tenon length and use a Keele reamer to make a new chamber. But some 'smiths do great stuff with great tools used in great processes.