For 600, I like the 223. I used to recommend the Savage 11VT from Dick's but I won't do anything from Dick's anymore; so I'll take a guess and suggest the
Savage 10T from Cabelas as being the effective equivalent rifle. For Optics, I suggest the
Mueller 8-32x44, and
Vortex Medium 30mm 6-Screw rings. This Mueller can resolve 22 caliber bullet holes at 250-300yd.
I'd say you're looking at about $900 for each setup. All of these items exist in my own inventory and have been in use for years without issues, so I can recommend them with high confidence. They represent almost two decades of experimentation intended to find a reliable entry level system.
I have two identical setups, a 223 and a 308, and despite the low cost, these are excellent beginner level training systems. They also quality for 600yd and 1000yd F T/R. Just add a bipod and it's ready for formal F Class Competition.
The 223 likes the HDY 75grain HPBT-Match and 23.7 gr of Varget, the .308 likes the Sierra 175gr Matchking and 42.2gr of IMR-4064. These are mild enough loads to spare the bores for a longer life, accurate, and adequate for the distances. These are what I think of as 'bread and butter' loads, plenty good enough for consistent performance while sparing both bore and wallet; and they leave some room to move up in performance when your own performance is up to that level.
The 223 is my recommendation because it's very economical to shoot a lot, which will be your first priority. It will be working harder at 600yd than the 6.5CM or the 308, and that's not so bad a situation when you're learning the wind.
Yes, velocity and BC can cheat the wind; but the more you cheat the wind, the less you learn from it. Learn on the basic load, and excel when you shoot the high precision stuff.
For beyond 700-800yd, the .308 will step up to the plate just fine; and the two can be shot in F T/R Comp to get your feet wet in formal competition. By the time you've wrung all of the potential out of these rifles, you'll be well qualified to move up to something more complex. With the Savage 308, you can spin on a second drop in barrel chambered for 6.5CM, and be ready for F Open.
Honestly, I think it'd be a shame subjecting a highly refined rifle to that beginner's learning stage. When you do move up, these rifle(s) will probably still have a bunch of life left in them and serve nicely as practice/trainers.
Greg
PS 7/28/18
Edited to add:
Rifling twists (and to a smaller degree, barrel lengths) are critical to longer range performance.
The bullets we like for longer distances tend to be longer (and consequently, heavier). In the .224 bore diameter, I have chosen the Hornady 75gr HPBT-Match, mainly because it works so well in the 1:9"twist, and I have been doing the bulk of my load development work as an effort to produce a generic MR/LR load for 24" barrels of both 1:9" and 1:8" twists (not as hard as I had expected; 75gr HPBT-M, 23.7gr Varget, BR-4, Starline Brass). Since I use it solely in my 24" length barrels, I can't say with certainty that it will work in that twist at significantly shorter barrel lengths, and there is some discussion suggesting it (the bullet, not the load) may not. I can't confirm or deny that. For altitudes below 4000ft, I have used 24.4gr of Varget at 600yd (and 1500ft) with moderate success. I would not try a longer bullet in 1:9", and have shied away from even the 75gr A-Max for that reason after reading several anecdotal reports that it wouldn't stabilize in 1:9" barrels.
Two of my 24" barrels are 1:8" twist and handle the 75 HPBT-M just as well. If I were to shoot 80grain or heavier/longer, I would be looking for the 1:7" twist, which will work, but may be faster than ideal for some of the (less) heavies. I have a new 16" 1:7" barrel and will be trying bullet weights of up to 77gr in it soon. I seriously doubt that there will be stability issues.
There is some thinking that a bullet may shoot at its best when it gets close to being too long/heavy for a twist. I have been trying that and not seeing much to disagree with it (i.e the 75 HPBT-M in 1:9").
Slower twists, like 1:10" and 1:12", are holdovers from days when lightweight bullets were the norm. The varmint rifles sometimes still have them, but they are less well suited for longer distances since they cannot stabilize bullet weights above 55gr-60gr.
