Hopefully Brad can help us Dean.
I agree that the distal segment of the right tube poorly matches the breech (thicker) segment. Tubes were usually made up from 2 or 3 segments.
This is a dramatic example of mismatched tube segments; a Remington 1900 KD with a clear transition (and weld line) from 'Oxford 2 S.J.' Two Iron Crolle at the breech to a 'Boston 2 S.J.' distally, on both tubes.
More examples here
http://www.picturetrail.com/sfx/album/view/18015717