2-p, I think you guess right. I'd be quite surprised if the 30" ers didn't swing a bit slower (higher MOI) than the 26"ers. Not because of the length per se, but because there is weight further away from the gun's CG. The increased balance point of the barrels and of the gun are proof positive of the increased weight forward.
Far as I know, there is no gunmaker who includes swing efforts in his specs. So, we are confined to doing our best in using weight and balance to get as close as we can to a desired MOI. Imagine that you had specified that the gun balance 3/4" back for the 30" barrels. Then, you might well have equal swing effort. This, of course, begs the question, "Do you want equal swing effort for both sets of barrels?" Are the barrels for differing purposes? If so, what kind of handling do you want for each purpose? It seems that you have gotten exactly what you want --- even if by accident.
My idea for developing information about swing effort is to allow shooters to give handling specs to gunmakers and thereby eliminate chance as much as is reasonable.
DDA
