I have worked with about 15 different rifles in a variety of calibers over the years but never had an experience like this fall. My pride and joy is an Interarms Mark X mannlicher stocked 7x 57. I picked it up used two years ago. Upon buying it I went the range with some PPU 139 grain ammo. The rifle cut 3/4 inch groups. I hunted the season with that gun and took a decent whitetail. During the off season I completely cleaned the bore for copper and powder fouling. Going back to the range the rifle was all over the place. I checked all the screws and nothing was loose. I went back to shooting and found the rifles accuracy return after about 20 rounds. I have always had to fire a fouling shot or two in a clean bore but never had one thar seemingly required a dirty bore to shoot well. Has anyone else experience this?