huskyswede,

The RCMs are not dead.

The RCM brass is still available:

300 RCM
http://www.midwayusa.com/product/17...s-300-ruger-compact-magnum-rcm-box-of-50

338 RCM
https://www.grafs.com/retail/catalog/product/productId/7082

As for rifles Ruger still offers both chamberings in the guide gun.