Whatever factory rifle you choose, in order to have some semblance of competitiveness at longer ranges pick one with a long heavy barrel. Preferably at least 26" long and a straight taper and without fluting.
Careful consideration of your scope and mount will also be necessary. Either go for a scope with a very wide adjustment range which will restrict you in the maximum magnification available or go to a tapered mount. With the tapered mount the scope will also need enough adjustment range so you can zero for 100 or 200 yards for example.
The various 6.5mm cartridges are the current fad calibers but that said who knows what the fad will be in a couple of years time.
I would suggest that the mundane, boring 308 would be the better option.