I have 2 5R's... One in a 24" .308 Win, and the other a 26" .300 WinMag. So, as long as Remington did their part, it should be a good shooter. My .308 Win shoots ¼" groups at 100 yards with handloads. Can't say about the .300WM, as I got it back around Thanksgiving, and still haven't even shot it yet.
They are the same exact rifle as the SFII, the only difference is the 5R has a 5R rifled non-fluted barrel. They both use the same HS Precision stocks, and stainless/jeweled barreled actions, and same factory trigger.
I would keep the Sendero 7mmRM, honestly. All of my Senderos are so close in accuracy capability with my 5Rs, and anything the .300WM can take in North America, so can the 7mmRM with equal-BC classed bullets. So, honestly, I don't think I would trade one for the other. I have found them to be on an equal playing field.