the case capacity of a 338 Edge is around 114 gr H2O , and a 338 Lapua is near the same
the capacity of a 338 RUM is very little less at about 108-9 gr H2O
assuming identical barrels and throating , there is no way an Edge is gonna beat a RUM by 300 fps
My 26 inch Lapua with 300 gr slugs tops out at 2700 fps with H1000 and maybe 2800 with RL33
there is really nothing to be gained by rechambering an RUM to Edge unless the brass is just much easier to come by in your locallity.......300 RUM brass is near non-existant in the USA , so is 338 RUM for that matter
