Not allways the rifle some bullets are bad that way. First original Barnes X bullets copper fouled bad enough to ruin the groups in 12 rounds in my mkV 270 wthby with 130 gr x bullets from factory PMC made Eldorado loads. Took a lot of effort to get clean. SAME thing happened in a lefthand 240 wthby mag with the blue coated x bullets. Stopped using the x period. I have some triple shocks now without the same problem but it sure soured me on Barnes bullets...mb
