I just installed a new willson 20" SS bull barrel and ran a cleaning patch with clip on it through the barrrel. The patch came out very dirty. I cleaned the barrel and then look at the barrel and saw what looked like copper fouling. I ran a patch with sweets copper remover down the barrel, followed with a dry patch. The dry patch came out blue indicating copper fouling? I clean all of copper out of the barrel and now I don't see any copper in the barrel.
Is this normal for a new barrel?
Does willson test fire there barrel?
The barrel was purchased new from M&A parts..
It's normal during a break in period of a new barrel for it to copper foul some. This will decrease markedly over time, then increase again gradually as the barrel wears out.
It may have been test fired before shipping, I'm not familiar with what M1S does.
Cleaning and properly lubricating a rifle is always the last step just before shooting for break in, as a general rule and a part of the final QC look over.
I'd say shoot it and see how it does. Good luck.