Looks like I missed out.
Years ago, when the WSM case first came to light, a buddy and I built 2 identical rifles on stainless Win Model 70 standard actions, not the short WSM actions.
Anyway, we built 25 Pronghorns, as they were known by then, and pulled our hair out trying to get a powder that would burn correctly in that case/bore. The ONLY powder that didn't soot the entire case and dent the body was RE25, even H1000 would not burn properly.
In the end, we both removed those barrels, I rebarreled with a 270 Weatherby and never looked back.
Funny thing, up until a few months ago, I had a rough chambered barrel in 6.5x284 Norma sitting in a sock for the last 12 years, I re-chambered it to 264WM at a finished length of 31", just for ***** and giggles, yet to fire a shot out of it, just had surgery on my carpal tunnel injury. So as soon as I can, I will be giving the 129gr ABLR & 142gr ABLR a run through it to see just how much velocity I can ring out of it.
I truly believe the 25-284 is a twin to the 25-06, which I have myself. The 115gr Berger is the only VLD I've ever used in my 25-06, very accurate bullet, so a higher BC and a heavier bullet can only be a good thing if you have a fast twist barrel.
Hope it works out for you.
Cheers.