My 581 mini 14 shoots two distinct groups. Shooting at 75 yds, the first 3 shots had one in the center ring and two up and right 4". Repeated the 3 shot group and same thing. And a third. I did not check or record if it was the first shot each time in the center ring, but think that is most likely the case. Figured to remove some wood and free float the bbl, but when I took it down i see a metal liner in the bbl channel. Any proven techniques to fix this.