Any AR-15 compatible chambering usable at 800-1,000yrds??

[kingcheese]

6mm, 6.5grendle, and a couple of uppers in 50bmg and 338, not really sure how the larger two feel with their recoil, but the 6.5 can reach out a long way

 

[Edarnold]

Another vote for a bolt action:
.243 Winchester with 105gr (A-Max) or 107gr (Sierra MK) readily handles ranges to 1K. Standard, readily available, low cost components in a proven caliber.
Start with a Savage Accutrigger short action from the cheapest rifle you can find, new or used. Add a 24" Shaw stainless varmint weight barrel with the 1 in 8 twist necessary to spin those long bullets for $200 plus fitting. Drop into a Choate Ultimate Varmint or Tactical stock for another $200. Add your choice of mount and scope and go shooting.
You get a roughly 12 pound gun that is well adapted for long range, has very mild recoil, and avoids odd-ball or proprietary components for a very reasonable cost. If you bought the barrel sleeve wrench, you can swap out barrels to try other calibers for the cost of the barrel.

IMHO

 

[Littlemac]

i have been successful in reaching out to 1000 yards with ar. i put a 24" shilen barrel chambered in .223 wylde and used 80 Nosler and Yellow box bullets. Not hard to do at all. You can see the results at NTSA when I went with him to 5 pts tx to shoot at that range

At 20 hits in a row on a man size targets not much of a challenge.

 

[AABEN]

The 6.5 is the best way to go. You can't go wrong.Read the Shooting Times Dec 2012 Jan 2013 it has a good wright up on the 6.5

 

[meanmrmustard]

Methinks a .260 rem would be grand.