I had a ruger 30-06 that did this as well. Since you already have the barrel free floated, and the action bedded, you can likely eliminate those issues, provided the bedding was done correctly. I am not an expert, but it sounds like you have a harmonics problem with the barrel. The harmonics on the cold barrel are diffenrent than when it has been shot and is warm. A couple of suggestions: if you reload, and are not at a max load, try going up .5 or 1.0 grains of powder. Also, if possible try and extend the bullet out in the case about .001. This may give you enough change in harmonics to "fix" the problem. I have a custom bartlein barrel and after 250 rds I developed a slight impact change on my first round. (about .5inches at 200yds.) I did both of the above, and eliminated the problem.Not sure why it took that many rnds to develop. I have also heard of people using those rubber dampners that fit over the barrel to change the harmonics. It may be a gimmick, but then again it may work. If your barrel is long enough, say 24-26" you could also have a gunsmith cut off 1" and recrown. This may fix the harmonics issue as well. On my ruger, I tried everything but cutting the barrel, and never did fix the problem. I sold the rifle. If these things don't work, either sell the rifle, or rebarrel it,because you will never have confidence in the thing. Good luck!
