I went down this road with my 30 SM and ultimately the 215 beats the 245 every time ballistically. It simply can't be pushed fast enough until you get into the 300 Norma or Ultra Mag case volumes. Id expect you to be around 2650-2700ish out of a WSM. A lot of it will depend on powders available as well.
240 grainer at 2.860" COAL is really stuffin it in there! I bet that Sierra has a fair bit more bearing surface and the OP has longer freebore so I suspect he could do a little better but still.. thats a lot of bullet for a wsm case.