Re: new to bolt action.need opinion
The 5r is a very nice rifle. Either caliber will shoot those distances, naturally with a ballistic edge to the magnum. Pros and Cons. Plenty to read up on there lol.
The 308 will help you improve your skills and be cheaper to run. It will make you call the wind better and may allow you to shoot better because of less recoil. If you are wanting a workhorse to train with, then I would pick the 308 (or a similar caliber, maybe a 260 or similar).
BUT the fact that you have an ar10 does make the 300 mag appealing, especially if you are wanting something new. If you are planning to go LONG, I would lean to the 300, but I don't think you NEED it until you really get out there a bit. For me, shooting the bigger mags do take a toll at a long range session... but that is just me.
Really just think out what you would like to do, goals/objectives, and I think that will help everyone give you better advice. Ie, hunting possible, ELR shooting, practical competition, training, cost concerns.