Maynard's right, no need for a monster caliber for only 600 yds, .308 would work quite well and depending on what type of matches your talking about they probably won't allow anything with a muzzle brake i.e. .338's or 50's.
50's are also cost prohibitive when it comes to shooting alot, due to the cost of the ammo/parts and the guns them selves. Also can be a challenge to get the supplies for.
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50s ARE spendy and not everyones cup of tea. They may not be the most practical rifle in many cases, HOWEVER when it comes to sure balls to the wall fun, there isn't much that can rival the blast 1 can have with a 50.
I don't seem to have any problem feeding my 50s for some reason
50s are like supercars, for most guys a Kia or a chevy is all they really want or need, but then there are some of us who prefer something more Ferrari-ish.
Not necessarily a daily driver, but you get the drift