I grab my .308 90% of the time. It will do everything I could wish for with cast of jacketed to as great a range as I can still see clearly, but there is no practical difference in performance between it and the .303 you are now using. (If you are going where the ranges are longer, borrow your brother's rifle. ) If I were just starting out today, I would probably go with something a little easier on the shoulder for longer sessions at the bench, (maybe in .25 or 6.5mm) but I didn't have the patience for a lot of testing when I was younger. I can understand you wanting something lighter to carry around all day than a SMLE, but the truth is, you may be hard put to beat its accuracy with a new rifle. I am not one to be at all impressed with the newest this or the latest that, and most of the rifles I buy are used (except Contender Carbine barrels). I am awfully partial to Mauser actions, but I'm happy with just about any decent bolt for a deer rifle, as long as it's accurate. Find one with a stock that properly fits you first, then worry about the chambering later. You can handload, so factory offerings mean little or nothing. The better it fits you, the more you are likely to practice with it. You could have a .458mag that will shoot one hole groups, but it will beat you up so bad that you can't pass the pieplate test at 50yds offhand and will end up gathering dust until you can find a sucker to sell it to. I would rather something more user friendly that will come to the range to be shot regularly and know that when I pick it up, I can hit what I'm aiming at.