I've shot severall rifles between 600 and 1000 yds. Here's my quick overview based upon myself being an average recreational enthusiast.
223/556 AR15 20" match service rifle. outstanding and economical at 600 yds when loaded with a 80 gr match bullet , zero recoil
R700 Varmint 26" .308 1-12" bbl, outstanding midrange caliber, plentiful reloading components best using 155-168 match bullets, mild recoil, awesome barrel longevity . (Not a good choice for a 1000 yd rifle from the slow barrel twist and length)
Savage 12 FT-R .308, 30" bbl 1-10 twist. This is hands down the best out of the box rifle you can use an midrange. My rifle has shown me .75 MOA at 600 yds (only if I had the skill to call "sub moa all day long", but I don't) . Unfortunately have not yet had a chance to try this rifle at 1K , but it certainly is capable by the numbers.
R700 Varmint 26" 243 Win, outstanding midrange , uses 6mm bullets , zero recoil , shorter barrel life. Excellent at 1000 yds, but the lightweight smaller bullet will be tough to spot at 1K if you are shooting steel.
R700 300WM 26" Sondero. Outstanding ballistics at 600-1000 yds, flat and fast. 180+ gr bullets will be expensive, basic sporter rifle will hammer you hard with recoil. Also shorter barrel life. I have Bell and Carelson T5 stocks on all my precision rifles and they add much weight, and tame recoil. My 300WM is fitted with a brake which also tames recoil quite a bit. I also wear a recoil pad and that allows me to shoot all day with my 300WM.