6.5x68 vs 6.5x68R

A question. Thef irst of these rounds is rimless while the second is rimmed. One for bolt actions and one for breakopen single shots.

Are they loaded to the same velocity levels?

The reason for my question is I have an attraction to get an affordable takedown rifle in 6.5x68 and 8x68S. A single shot rifle with 2 barrels may be a possibility. But if the 6.5x68R is downloaded I would not be interested as the ultra-velocity is what I am looking for.

I also find it interesting that gunmakers chamber the rimless 8x68S but chamber a 6.5x68R instead of a 6.5x68 rimless (???).