I think the RSM refers to the Magnum rifle made on the Tangs Safety action. It does have a plunger ejector and of course a true CRF affectiondo would dis it as unworthy of dangerous game. I owned one of these in 416 Rigby and it was a fine rifle, a bit heavy but very nice with excellent build quality.
Ruger also made magnum rifles in the MKII line, I think they were called the MKII Deluxe Magnum Rifle and were pretty much classical CRF rifles. I never held one so I can't comment on its fit and finish, but I would guess that with a check-up and a massage from a good CRF smith, these would make a fine dangerous game rifle.
This is incorrect. Ruger did not make the RSM "magnum" rifle in the tang safety, only the Mark II. There were 458 mag caliber rifles made in the tang safety but with the standard M77 action, not the RSM magnum action. He talks about those too.
Here is a link to the article:
http://www.africahunting.com/content/2-big-game-hunting-rifles-500/ 
