Yes. Nothing against round balls as slugs.
Just a round ball which fits in an 12 ga wad is of about the 7/8 oz Lee drive key slug size. That slug is .681" of Diameter. A round ball of .680" Diameter will have an weight of 473 grains.
All I say is that is to much of recoil for me myself. And I read on the Internet there is an ever groving mass of People who prefer the 20 ga over the 12 ga because of reduced recoil. They migrated from 12 ga to 20 ga.
The .575" Diameter round lead ball fits perfectly in an (most) 20 ga wad. And that is about 283 grains.
The Lee 7/8 oz drive key slug is 383 grains.
Compared to that the 12 ga .680" round ball is 473 grains. That is 100 grains heavier than the Lee slug and 200 grains heavier than the 20 ga lead round ball.
I shot already the .575" round ball out of an 12 ga Shell and it has almost no recoil but is not accurate as far as I can tell (shot out of an open choke Maverick 88 security gun using the Black Powder and the powder of 1 bomb of an rocket from an distance of 40 meters).
The 12 ga gun I have is this:
From Website (Source):
http://www.mossberg.com/product/500-turkey-53265/
You can not say the gun does not fit me since it is completely adjustable. Same gun in 20 ga has just arrived for me. All my guns have adjustable stock in order to fit perfectly.