My accuracy in that barrel was poor with Hornady 55 gr fmjbt's and with wolf 55 and 62 gr ammo.
When I went to the hornady 75 gr fmjbt's it shot like a champ.

Here's another guy with a different 1:7 gun that had the same experience:
AR15 had a chrome-lined 1 in 7″ twist barrel. It was freakin’ picky on ammo and preferred match stuff in the 68-75 grain range (Ultramax, Prvi, etc). With those heavier bullets I could turn out some 1-2 moa groups. After break-in I was quite pleased this rifle with the M4 profile 16″ barrel turned out a 3″ group with Ultramax 68 gr at 300 yards. However, with various types of 55 gr ammo (Federal, PMC, Wolf) my groups ran anywhere from 5″ to 7″. This is like a car that prefers premium gasoline to “run right”. I’ve shot many other AR15s with 1 in 9″ twist barrels which have grouped everything in the 55-75 gr range far better.
http://gardenserf.wordpress.com/2011...-vs-5-56-west/