M117LR is the current sniper ammo and can be found here and there (175gr Sierra HPBTM)
M117 is the older flavor (173gr FMJBT) which can't hold a candle to anything with a modern hollowpoint match bullet. It's slightly better than M80 ball accuracy wise (maybe not depending on which mfgr and lot# you are talking about), but it will fly flatter and buck the wind better at 600yds and out.
M852 isn't made anymore, but it's good stuff (168gr Sierra HPBTM--any commercial 168gr match is an equivalent of this)
Radway Green is Brit M80 ball that has a good reputation for approaching match accuracy. I'm not really familiar with the other various M80 mfrs to tell you what works better than others. I know a lot of expert class shooters that use surplus ball with pretty good results. It will shoot reasonably accurate to 600yds, but after 300yds it starts to get blown around a lot by the wind and it isn't competitive against any of the match grade bullets. But for beating up steel gongs and paper plates at 300yds and beyond, it should be more than adequate.
Any match bullet (besides the military 173gr FMJBT which is touch-and-go) will be 1MoA accurate out to 600yds out of a tight rifle. The 168's are a good all-around match load, but the 175 has an edge at 600 and beyond.