My first inclination would be to take a peek at the CZ 527 Varmint models. They come with rock solid proprietary rings, a single set trigger (un-set is usually around 3-3 1/2lbs, set stage is around 1lb give or take an ounce or two), they have generous palm swells that weem to work equally well for righties or lefties, free floated bbl's. I can't recall at the moment if the newer models come with 1:12 or 1:9 twist barrels, but that should be of little concern at 300yds as 55 to 69 grain bullets will/should do just fine.
I have both the 527 Varmint and the American models, and I can tell you- they have been the best money spent on rifles that I can claim. I load mine a little on the warm side, mag length, but with only 55gr bullets. I have never had a problem with loading, firing, ejecting. Nor have I ever had any problems with the rings going loose, or adjustments in the trigger mechanism going squirrely.
CZ has a healthy following here- check the search feature and see for yourself. That might be good medicine for me too- as I started to write that no one has admitted a dislike or hate towards them. But it might just be that I haven't personally seen a flame towards that line of rifles yet.
Anyway, glad to see folks who still do some earnest research before taking a rifle buying plunge. As much as I endorse the CZ's you might well decide they aren't right for you after all- at least you can say you made a well researched decision regardless of which rifle you go with. Have fun, good luck, and good shooting!
Edit: I just peeked at the CZ website, and it does appear they sport Varmint barrels in 1:9 twist.