Mike,
I don't know who made that gun, but many,[especially American], makers put their 410's on a 20ga. frame. In order to make this work, the outside diameter of the barrels was basically that of a 20b. Since the bores are 410 size, this leaves a very thick wall, making the centers fairly far apart. The more distance center to center at the breech, the more required for proper convegence at the muzzle. Based on that picture, I'de say that's a fairly heavy 410. I looked closely to see if there wasn't any rifling in the bores.
Luck,
Jim
