Thanks all for the good advice.
I measured the outside diameter of the barrel with a micrometer and found a slight bulge; looking into the BBL I cvan now see a slight ring inside. That would appear to be the problem. I have no idea how or when that could have occurred but I will be ordering a new BBL shortly.
Has anyone have a preference to after market 45ACP 5" BBL?
"The Constitution is not an instrument for government to restrain the people, it is an instrument for the people to restrain the government, lest it come to dominate our lives and interests."
Patrick Henry, American Patriot