Carl,
I would very much like to talk to the man who did work on your barrels. He might know if here was evidence that they had been previously honed before he received them. Also did they measure 0.751" or so at several places along the bores, or only where the pitting was worst. If so the pitting could have made 12-bore barrels into the 11-bore range.
However, if they were originally bored to the .751" dimension, then the gun was made an 11, even if Parker may have chambered it for 12gauge shell and called it a "12". It is well known throughout the world that it is the bore dimension and not the clambering of the gun that determines the gauge size. If you call a lemon a pineapple, it will still not be large and sweet.
But it is clear that the Stock books contain many discrepancies in this area. I have an early lifter D-grade 11- bore Parker ~0.755" with 30" barrels that was chambered for 10 gauge shells and is listed in the Parker Serialization as a 12 gauge with 30" barrels. If the stock book listing were based on the chambers, then this gun should have been listed as a 10 gauge. However there is clear evidence as Austin Hogan has pointed out that Parker over bored many guns in the 7000 to 70,000 range. The question that needs to be answered is --- Why? They clearly knew how to make perfect 12-bore barrels as we heve found in many early guns with .729" bores. Could it be that they did this to reduce the pressure that may have helped reduce failure in lower grade barrels? To answer this, we need to find out if there are any written factory memos, letters or records that may solve the Problem. Austin mentioned a King patent for tooling that caused the barrels to be overbored, but I have not been able to find it. The only one I remember having in my collection of Parker Patents related to a method of encasing the barrels in Plaster of Paris to keep them from vibrating or twisting during the boring proces, but that would not alter the bore diameter. If anyone could upload the King tooling patent, I would very much appreciate it, as I am still trying to understand how to unravel this mystery. Also, it would be interesting to know if thare are many 12-gauge barrels in this serial range that are bored .729", and if so are they also on the lower grade guns.
Please put me in contact with your barrel man, as he might have some answers to these questions.
Yours,
Richard