I went to the range today to try to zero in my new ar. Just to preface I am a veteran shooter who reloads for my bolts and get 1/2" groups with numerous rifles. I was shooting my bushmaster xm 15 that I just got about two weeks ago. I did break the barrel in with the 1 shot-clean method for the first 20 rounds on a previous visit to range. So today I shot it at 50yds to sight in my new scope. After that went to 100 where my first 3 shot group was about 4". I continued to shoot with allowing 2 minutes between shots (it was 35 degrees here today). Total group for about 25 rounds was 5". Then I took some fast shooting to have some fun. I then decided to try to group again. I ended up getting 3/4" 5 shot group. Has anyone else had anything like this happen to them or any ideas why my group was amazingly better with a warm barrel? By the way I was using cheap steal casing ammo in 55gr.