I have had feeding issues with my 6.5 CM using longer high BC bullets. They are loaded to easily fit the magazine, but still don't reliably feed. Especially the 1st or 2nd round. If the magazine is loaded with 2 or less rounds they feed just fine. I had the same issues with both the original rotary magazines and the newer 4 round staggered magazines. My solution was to buy a 3 round single stack magazine made for the 450 BM. With that magazine it feeds just fine with any bullet that fits in the magazine.
Ruger Mag Ruger American 450 Bushmaster 3-Round Polymer Blue (midwayusa.com)
These feed 308, 7-08, 243, and 6.5 CM rounds even better than the standard magazines that come with the Rugers. You do give up 1 round of capacity and they do extend slightly below the stock. But is worth it to get a better magazine. I think this is a big reason Tikka's feed so reliably. They have always used single stack 3 and 5 round magazines.
My 308 Predator uses the AI style magazines and the 223 uses AR magazines. Never any issues with those.