I got my new issue of guns magazine yesterday and on the cover is Les Baers Varmit AR.  The authors claimed that out of 30 sets of 5 rd groups, the rifle's best group was .26", the worst was .67", and the average for 150rds was .47" at 100yds.  Now I don't exactly believe everything I hear but that is amazing!
All the shots were fired over a two day period in North Dakota in temps at 3 deg. above zero.

If you get the chance, get the magazine and read  the article.

Most any stock AR I have had will shoot 1" groups from the box. Any custom one should shoot better.

A local gunsmith builds these up as linked.

[url]http://www.hatchergun.com/ar15.htm[/url]