why 12 ga slug and not, say 45-70?
Because I wanted to build a 12-bore rifle and I didn't want it to weigh twenty pounds.
A .45-70 with the barrel contours of a 12 gauge gun would be very heavy and if the rifle barrel contours were small enough to effect a reasonable weight the rifle would suffer aesthetically.
Besides, the .45-70 conversion is the go-to conversion so I didn't want to go down that path.
Even though the .45-70 is a low pressure cartridge by rifle standards, most if not all factory loads far exceed 12 ga chamber pressures.
