I have excellent results with Sierra 69 MatchKings, which will usually shoot in anything with a 1:9 twist and faster. As loaded by Federal (Gold Medal Match), they shoot 3/8 moa or better from my 20" 1:7 Wilson barreled AR and 1/4 moa from my buddy's 24" 1:9 Krieger barreled AR.
Heavier bullets require faster twists, but will remain stable further out, resisting wind better and dropping less than lighter slugs. There are several match bullets offered by various manufacturers. The Sierra 77 MK is used in the current M-262 long range match load, and is loaded by Black Hills. For slower twist barrels that won't like heavy bullets, the 52 SMK is usually a good shooting bullet, and Nosler's 55 Ballistic Tip shoots well in a wide variety of rifles as well.
What twist rifling do you have?