Here's one you don't see every day: a 20 on a 16 frame. Nice combination.
Classic example of what I am questioning.
I would like to see a photo of the open breech, straight down the chambers.
To see the chamber wall thickness & distance between centres.
O.M
A couple or 3 examples of what you are asking to see would be:
A Crescent Quail Hammerless 410 would be 20ga wide, and 410 barrels. The breeches are extremely tapered down to the barrel diameter.
A Browning Citori 28ga, they are made on a 20ga fram, and weigh more than a 20. Externally they are identical to a 20. So, the chambers show extremely thick walls, same primer centers as 20ga. And, just about every multi-barrel set, they will have the firing pin centers (the common dimension) for the widest bores, and the other gauge sets have to match them.
Which brings me to Don Amos' brilliance.
The handling dynamics of shotguns with much of their mass concentrated around their balance point is now measurable.
Thank Don for that.
With whatever frame size, trigger spacing, etc, that you desire, you can measure the handling dynamics your shooting style requires for your success.
