After looking at the SAAMI Drawings, it looks like the Weatherby will clean up the WM chamber. Still a good idea to let the gunsmith decide if the barrel needs a set back to clean it up completely.

Here is the link to the 300 WB drawings
http://www.saami.org/pubresources/cc_drawings/Rifle/300%20Weatherby%20Magnum.pdf

And here is the drawing for the 300 WM
300 Winchester Magnum
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcSPhggAVsaBlqEgZikdgmEkVd6Cc0Cv3LFM1SA1cFKETTAFcv9Y






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