I'm not 100% sure but I'll take a stab at it. I believe Winchester uses the same action on 300 RUM rifles that they use on their Safari Express line. The reasoning is the Safari is chambered for the big long dogs such as .375 H&H which is too long for the standard long magnum action. The standard long magnum action accomadates up to .300 Win mag which has a saami overall cartridge length of 3.340, same as 30-06 and so forth.The saami overall recommended for .300 RUM is 3.600. Plus I think the opening in the action itself is slightly longer.So to answer your question screw to screw measurements would be the same, but the Ultra mags box is slightly longer. I actually took the wood stock offmy Sporter LT .300 RUM and used it on my M70 stainless .30-06 one year, bolts lined up and itshot fine.But thestock had excessive room going fromlong express magnum box to standard length. If you get a stock for standard longactions you might have to openthe box area upa bit, could depend on stock manufacturer.