I think the plastic shot cup would work the same as paper or mylar cups to keep the lead off the bore, although that has never been my objective.
Indeed. But you closed with saying you were going to take the cups out. I think the paper might help if you do. Depending on the paper you use, it could also reduce shot deformation along the bore's wall. Anyway, just a thought you might try. I'm always interested in BP loads. I've had trouble with plastic shot cups over fiber wads. For some reason they still melt onto the bore walls and make for tedious cleaning.
I've been using PB loads as described above for over 15 years. I only had plastic melt in a barrel once. It was a hot day perhaps 90F, the gun sat in the sun at a trap range for an hour then I ran 50 loads through it fairly quickly. The shot cups melted inside the barrel at the chokes in long strings. I've never had anything even close to it since and quite often examine the shot cups when I find them on the range or in the field.
But back to the patterning. I used the Baker today in a pheasant Calcutta. Perhaps new gun syndrome but I couldn't miss. I was somewhat surprised at hitting many in close range.
