6.5 creedmore on an AR 10 lower is the best long rang paper puncher, purpose built for long range accuracy! Its terminal ballistics aren't great at 800+ yards. Really need more rifle if you want to do more than punch paper at that range. 260 rem , 280 rem, 338 lapua, 300 mag and 308 are other possibilities for long range work. Higher grain weight= higher energy on the target=increased recoil.
The best long range rounds in the AR 15 are the 6.5 Grendel and the 6.8 SPC. Both are "useful" 500 yard hunting cartridges, sufficient vel/energy at this range. They can punch paper at 800-1000 but are marginal energy at this range. Pretty much anything that fits an AR15 mag is the same boat. Ssgn_doc's advice on high weight/ length bullets is spot on! A 223 custom load can reach but wont kill at these ranges.
Long barrel is a must 22-26", so are free float handguard. Serious optics needed at this range, $800+ on glass alone.
If you are serious about long range look into reloading, most of these rounds are $2+ a shot! The amount of practice ammo that you'll need to get comptition level accurate will easily set you back $20-$30k! The gun is the cheapest part of the equation.
A good bolt gun in 300 win mag will do the range you want much more economically. It will also be more accurate than the AR. Something to think about!
How much experience do you have in long range shooting? Are you just getting started? Do you have anywhere that you can practice this kind of range? Experience level Makes a helluva difference in what you need!
"You know why there's a Second Amendment? In case the government fails to follow the first one."
-- Rush Limbaugh, in a moment of unaccustomed profundity
"No free man shall ever be debarred the use of arms. The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
-- Thomas Jefferson, 1 Thomas Jefferson Papers, 334
"MOLON LABE" - Come and get them, can't be any plainer than that!
Last edited by dwmiller; 11-04-2013 at 04:52 PM.