Re: 338 Lapua Brass compared to 300 Remington Ultra Brass
Can't answer the original question due to the points that were already made..... way to many variables to consider to accurately answer with any certainty.
But would like to make one point on the comment about, if Norma started making RUM brass your life would be better. I say it wouldn't be better, just more expensive.
The Norma brass (assuming it's made like the rest of their stuff) would open up primer pockets faster than any Remington brass I've ever dealt with. So you would end up with really good quality brass for measuring purposes (weight and out-of-round would be many times better than Remington), but case life wouldn't be better and would probably be worse. Norma brass typically is the softest of any brass I've ever used for numerous chamberings and wildcats. It's the best stuff in the world when it sits on a scale or next to a dial indicator, but then you fire it and it goes down hill.
This has been a problem for many years, and Norma has never changed it. There was hear-say a couple of years ago that Norma changed thier process for "magnum" brass to toughen it up some, but newer batches of Norma brand 338 Lapua brass hasn't proven this to be true in my tight chamber.