Theory.

Here's a little bit of theory behind my rig. Basically my idea was to come up with a "stopping" gun. And while I didn't have anything against hard lead slugs, I just thought a copper one might work just as well, if not better. It turns out that this idea of a 12 gauge stopping gun is actually 140 years old, and goes back to the old British 12 bores of Africa. These guns tended to fire (in a 12 bore) a 600 grain round ball at around 1100fps. So this idea isn't an original one.

Secondly, a lot of guys were wondering about pulling a slug load out of "thin air". Well it wasn't quite that easy. I literally spent days reading old load data, querying experienced shooters, and reading books by WW Greener, Sam Baker, and all those old boys, trying to get an idea on loads and pressures. So the following is a comparison, showing my logic and reason:

Approved Load
-Federal 3" Paper base hull ---> Low pressure hull
-Fed 209a Primer ---> Hot (hottest) primer ---> High Pressure
-38 grains Blue Dot
- WAA12 white wad ---> Low pressure wad
-1 3/8oz lead shot ---> High pressure (compared to slug)

This generates 8800psi, and 1300fps

My load
-Federal 3" paper base hull ---> low pressure hull
-CCI 209 Primer ---> low pressure primer
-42 grains blue dot
-WAA 12 wad ---> low pressure wad
-580 grain Hansol Slug ---> My slug is 1 1/3oz, so is lighter. Plus, it's a slug, so using the rule that a slug gerates less pressure than shot ---> Low pressure

As for black powder loads, I came across the following stats in the Dangerous Game Journal, based on a 12 bore shooting a 600 grain round ball using black powder:

82 grains powder = 5350psi
110 = 6850
137 = 7800
164 = 9650
191 = 9750
220 = 11400.

I can't find any sources to verify the above black powder loads in a shotgun with charges higher than 105 grains, so haven't tested any higher loads. I don't like relying on just one piece of data. So I wouldn't recommend anyone basing their loads on the above stats until you can get something to cross reference.