Remember, unless you shell out $3000 +, for an M21/M25, you are going to have to shell out some serious coin to scope your M14 style rifle - they are simply not the easiest rifle to scope, and it shows in the price of mounts and optics that work well with the platform.
Although it is not totally in your line of questioning - I do a have a little experience with this question. About a year ago, I was desirous of a accurate, long distance capable rifle (preferably in .30 cal) and my mind went first to getting an AR-10 (actually, my first thought was to get an AR-30 in .338 Lapua, but I just couldn't justify the ammo cost with my current lack of ranges beyond 200 yards).
I was thinking about the AR-10 and pricing things out - and in the end I was looking at shelling out almost 2 grand between the rifle, mount, and optics.
I scrapped the AR-10 in favor of a Savage 10FP in .300 Win Mag.
Yes it's a bolt action - and yes, it is in .300 Win Mag (which IS a military cartridge, many militaries use .300 Win Mag in Designated Marksman rifles), and I ended up spending less than $700 for the rifle, scope(Super Sniper), mount, and case (to be honest, the rifle had been fired a few times, but that was mitigated by the McM stock).
I initially scoffed at getting a bolt action, but I'm as happy with this rifle as I am damned near any of my purchases, and I feel very comfortable with the rifle (especially the magnificant trigger) and I do not at all regret getting a bolt action over a semi auto..