I thought that the Ruger proprieitory cartridges were an idea looking for an answer when they did it.
A FEW of the WSMs have worked out and become succesful and even fewer WSSMs. Almost NONE of the RSUM or RUM have been very successful and it sure doesn't seem like many.any have made the transition over to being widely chambered by a variety of manufacturers.
The 204 Ruger filled a niche and has become successful across the board and is now chambered in a bunch of different rifles. However, even that has a limited market as the disconiuance of the #1 in everything other than the "B" sort of shows.
The marketing guys got the brain wave, HEY we can make money on both ends if we do these propriatory cases. Heck it worked once.
The problem is they are filling niches that simply don't exist and nobody has made a cartridge in the last 100 years that really made it UNLESS everybody ends up making rifles for it and chambering for it.
All you have to do is look at Newton, Lazeroni, Dakota and even Weatherby to see what happens when you build your rifle around a cartridge that only you chamber and that isn't popular enough to force the other guys to chamber it.
Heck, even Weatherby finally had to offer the MKV in standrad rifle chamberings to stay in business. The market just isn't big enough to support this any longer, if it ever was. UNLESS you want to be the maker of high dollar custom or semi custom rifles for a few rich guys.
I personally look for most if not all of the RCMs to drop off the charts in the next ten years, and I be suprised if it takes that long.
So, if I were to buy one I'd make sure I had lots of brass and components and don't even think about the down side when and if you ever decide to sell it.
Unless you find another RUGER guy that you can convince that this is the cats meow, your going to have a hard time moving these rifles in the future regardless of the cost.
My pennies worth.
Ross