Gary, In going back and reading this post, I couldn't find anything different in the two Longrange 3" guns I have to figure out what made these guns pattern at "longrange". In Brophy's book and in John's book it states 12 ga. bores were .728-.729. but does not state anything about Longrange guns bores etc. I made up some bore gages ranging from .722-.735 and found out that both of my Longrange guns are from .725-.728.and that they will go 27 1/8"-29 7/16" into the barrels. Both are 32" barrels. The only 12 ga. that I found out to be different in bore sizes is a circa 1919 where the right barrel started: .728 12 7/8” . .727 26 ½” .725 27 ½”
left barrel: .728 6 ” .727 11 ½” .725 11 ¾” .723 .001 was added to these readings for actual size of bore, could be .0005 or more. Ideal readings and accurate readings would have to be a ball shaped gage
So it definitely shows a tapered bore. All the other 12 ga I have done this way are more uniform and closer to .728 and lower.