it's a personal choice, but I'm not a big fan of 6mm and deer sized game at over 300 yards. I'd suggest a 25 cal-7mm range. However a well placed 243 round still kills game. I read here one place that rugers were really highly valued... as garden stakes lol! just kidding ;)
there will be a big difference in recoil when you add weight. some of my choices would include 25-06, 257 roberts, 6.5x55, 260, 270, 7-08. You may want to just take a look at a recoil calculator for a while and compare different calibers in various rifle weights to see what difference you will have. A good limbsaver or similar recoil pad is good too as is a muzzle brake
. but brakes are LOUD!