Have one that I could not get sighted in when I got it. Called Ruger and they sent a label to ship it back and check it out. They had it about a month but called before they sent it back they test fired it and shot under .5moa. It is super accurate now but they polished the feed ramp and did a lot of work to it a Ruger. I don't remeber everything but I think they changed the barrel and I know they changed the rear sight.
My SR 556 went from shooting 1"+ groups the first year I had it to shooting shotgun 100 yard patterns literally over night. One day it's fine, the next session shotgun groups. It's at Ruger now.