This one regulates with 1 sight using 100gr. or 110gr. 2F. The light charge shoots into one hole at 50yards while the heavier charge shoots perfectly parallel. From what I've seen, this one is an annomoly because it regulates to one sight. The 'first', folded sight, is zero'd for 200yards.

I know of nothing larger than .58 calibre in a production rifle.

You may find a custom gun of larger bore - probably smooth bore in .62 cal. - or 20 bore for under $2,000.00. That's about it. I don't know of any single 12's or larger. That isn't to say there aren't any- I'm just not aware of any.