http://www.2-bore.com/
The caliber equivalent of 2 bore (‘bore’ is generally interchangeable with ‘gauge’ in regard to caliber) is 1.326″ or 33.68mm! The bronze solid bullet weights 3500 grain / 1/2 pound / 226.80 grams!
While technically fired from a rifle these are more like massive shotgun slugs: a heavy projectile at a low velocity. The 2500 grain bronze solid leaves the barrel at 1500 ft/s and with 17487 ft·lb (23708 JOULE) of energy.
http://www.youtube.com/watch?v=eXoa5zNn0TU
http://www.thefirearmblog.com/blog/2008 ... r-express/
.500 S&W, .45-70, .700 Nitro Express, 2 bore
9mm Parabellum vs. S&H 2-Bore.
.700 nitro express next to 2 bore and 3500 grain bronze solid