I also am intrigued by large bore guns.

I have had 10 gauges and recently I built my own four bore (4 gauge) Blunderbuss. That has a bit over 1 inch in diameter bore. A 12 gauge bore diameter is about .729 inches to give you some appreciation for how large this bore is.

The round ball it shoots weighs over a quarter pound. (over 1500 grains)

I also shoot four ounces of #8 shot in it, and although I have not counted them, the tables tell me that should mean about 1600 pellets... per load...

There are A gauge which is 2 inches in diameter, 1 and 1/2 gauge which is 1.459", 2 gauge which is 1.325" and 3 gauge which is 1.158".

Between the 4 gauge and 10 gauge there is the 8 gauge which is .835" diameter.

My favorite gauge is 12 gauge. So versatile and you can load it up or down to suit virtually any need. But I also am fascinated by any that are larger and have settled on the 4 gauge for my big boy. It is a hoot to shoot. I have loaded it with 160 grains of 2F black powder under 4 ounces of shot and it has a commanding communication to the shooter.

And, I would NOT want to be on the receiving end.