Mike, I have to believe the tubes are straight unless a mistake was made by whoever stitched them together. If they were anything but straight there would be reams of material written about the fine art of bending them and then the incredibly difficult task of joining prebent tubes. There is nothing. In your discussion comparing 26" and 30" barrels have you considered the difference in barrel flip? Seems to me the shorter the barrel the greater the flip and vice versa. In my way of thinking that could easily explain how these two different lengths with very different convergence points still shoot to the same POI at distance. To reinforce the concept I have heard that guns firmly set in a bench rest shoot vastly different than shooting offhand.

John McCain is my war hero.