I have a Mark V in 270wby sporter that I never use as I have lighter hunting rifles, but I shot my first elk with it so I don't want to sell it. I'm thinking of transforming it into a heavy barrel switchbarrel. One in 7RM and one in a 338 cartridge, I'm currently thinking 338 RUM. The use will be long range practice with maybe elk hunting. I'd order two CM barrels, around .8 to 1" at the muzzle. A local gunsmith built it as the 270wby. He said he could set it up as a switchbarrel. I'll get an inexpensive Mark V stock as I'll have to really open up the barrel channel. Will a single Mark V action feed these 3 cartridges reliably? (270wby, 7RM, and 338RUM) I could go 270wby, 7wby, and 340wby; but the brass cost is out of control. The 338RUM seems to be the best value in big 338s. I already reload for the 7RM. Anything I'm missing? Other thoughts?