I have found that rarely is there a question that has not been asked before. So here goes. When you take a 2 1/2" chamber and lengthen it 1/4 of an inch to 2 3/4". How much barrel thickness do you lose, in comparison to the same make and model and gauge that is factory chambered for 2 3/4" shells? I measure a few 20 gauge barrels and the outside taper of the barrels drops about .020 to .025 in 1/4 inch. I believe this would mean that the barrel thickness from the taper alone would lose about .010 to .012. Then again the inside diameter tapers down a little smaller going from a chamber diameter to the forcing cone and then down to the bore size. On a Parker 20 gauge it goes from .698 ( Chamber) to .685 (Cone) to .615 bore. I am using Chamber and barrel bore measurements as listed in the Parker story page 519. I am guessing if Chamber and bore diameters stayed the same with later guns that the only thing Parker could possibly do if lengthening the chambers 1/4" is this critical, would be to make the barrel blanks larger or change the outside taper. I am sure I must be over looking something.
