I stumbled across the fact that the new Beretta 692 has 14" long forcing cones:
"Also, the OptimaBore Steelium barrels have a super-long (360 mm) forcing cone--meaning more durability, increased shot consistency and accuracy, and lower felt recoil and muzzle rise."
http://www.beretta.com/en-us/692/Say the diameter of a ten gauge bore is 0.775 inches. And say the diameter of a 12 gauge chamber (towards the muzzle) is 0.792 inches. Say the bore diameter of the Beretta "OptiumBore Steelium" barrel is 0.740 inches.
If the forcing cone is a true cone:
# It would appear that the diameter of the forcing cone is larger than the diameter of a ten gauge bore for about four inches into the forcing cone
# How can the wad stay straight?
# Why don't they just put a 12 gauge chamber on a 10 gauge bore and do away with the forcing cone?
Doesn't one of the clay shooters here (Stallones?) shoot a ten gauge with 12 gauge chambers?
Has anybody here every measured a "OptimaBore Steelium" barrel with a bore gauge?
The marketing guy that came up with the term "Steelium" should be horsewhipped.