Hello My friend recently fitted a new 28 inch barrel to his 243, 1:10 twist. He usually reloads and the previous barrel shot sub MoA groups at 200 yards with a 24 inch barrel. The bullets he was using was 87 V MAx with winchester brass. The rifle is fitted with a Leupold VX3. He broke in the barrel by cleaning the barrel after each shot and letting it cool properly. He shot 20 bullets through the barrel after he decided to site it in. The groupings are sporadic at best. He would group 3 shots and then it would start going everywhere. The problems he has considered are the following: The gunsmith may made a mistake with the fitting of the barrel and it will be taken in shortly. Problem with brass which will be replaced with Norma brass. What other problems can there be? He is a good shot and quite meticulous when reloading. Can the bullets be too light or too heavy for the twist? Any suggestions will be highly appreciated.