Has anyone any experience of a gradual deterioration in accurracy in micro groove barrels caused by copper fouling? I have now put about a hundred and twenty rounds of 265g Hornady XTPs through my 444SS and a recent careful range check has confirmed that the group size has opened up threefold. I have just done a thorough clean with solvent and, unsurprisingly, the bore was very dirty. I had been using a boresnake, but obviously this wasn't going to remove much copper. I haven't been able to get back to the range yet to check results. Should a good clean do the trick? Or should I be looking elsewhere? I'd appreciate your input. Thanks.