Yes, I hear you, however your comparison to the wildcats, 6.5-284 and 22-243, is not valid. The 300RUM was introduced as one more competitor for the top slot, .30cal cartridge. Had anyone been warning, early on, how finicky the 300RUM was going to be, in terms of OAL, primers, propellents and bullets, I doubt that the cartridge would've gotten off the ground at all.
I know of too many hunters who have for years, gotten excellent accuracy from the 300WinMag and the 300WeatherbyMag, without test firing eight or nine hundred rounds, before hitting on a formula that produces accectable groups. So, bottom line being, that if one has to sacrifice 200fps to get a cartridge that likes more loads, what is the big deal. Forget the 300RUM and go with proven performance in a cartridge, for which acceptable groups come easier. I am happy for those who have struggled through finding what works with their particular rifle, and are getting great groups with high velocity loads, out of their 300RUM. Some folks enjoy working through that particular exercise and I respect that. I simply believe that as a production cartridge, the 300RUM will not be with us long. This, not only because of the difficulty of finding acceptable fodder, but because of short barrel life that goes along with high velocity in big case magnums.
Even if we accept rebarreling at 1000-1200 rounds, are we to assume that the cartridge load search must begin all over again?
I received lots of help from bigcountry and others, when I was struggling with my Browning Stalker in 300RUM. I really do appreciate the time that others took to help me. bigcountry offered to go to the range with me and take a look at things and again, that sort of kindness is appreciated. However, I did not have it in me to continue with that cartridge and since I was able to sell with very little loss, the 300RUM went down the road to someone else. I have loaded well over a dozen high powered cartridges in the past and have never been so frustrated as I was with the 300RUM in that Browning. After reading of others' problems with the 300RUM in various models of rifles, I had to discount any problems with the Browning and lay the problem on the cartridge. I have held a dealer's FFL for many years and hear countless stories of difficulties, from hand loaders. Nothing matches the numbers of bad reports that I have heard, regarding the 300RUM's hand loads being hard to find, with acceptable performance.
Add to all of that, the fact that the 300RUM has no draw, in terms of being the biggest, badest, fastest .30cal. Some have said that not everyone can handle a high priced sports car and that they need to drive a Chevy. Well, the 300RUM is at best, an Edsel.