My .223 did not tighten up until several hundred rounds through it, and then only with premium bullets. I have cleaned the copper out of mine twice now (well over 2000 rounds). Each time it takes about 50 rounds to settle back down again. And, the telltale streaks of copper in the bore are there as it shoots 1/2moa groups. Tomorrow I am going to try a milk jug challenge at 1000yd with it.

My 12BVSS in .308 was worse. It finally became a 1 MOA rifle after about 400 rounds. It is more sensitive to copper so it got cleaned out after every 50 rounds. That was when I discovered KG12 to remove copper. Now it is my cast bullet rifle.

One thing I did with the .308 was to use Iosso paste on it several times. That helped the groups and copper significantly.