Hello;
Sorry for the late reply, but I just found the thread. Yes, 12 gauge slugs can be reloaded....I've molds for both the LEE and the LYMAN 12 gauge shotgun slugs; the LEE is a foster-type slug with a 'driving band' on the inside...the LYMAN is a wasp-waisted style slug. The LEE comes in 7/8 and 1 oz weights, while the LYMAN weighs (IIRC) 1 1/16 oz.
Both are loaded in a plastic shot cup (they take the place of the shot), and can use a folded crimp, which makes things a bit easier. I haven't used them, but you an get Gulandi dangerous game slugs from BPI and load them with a roll crimp.
Both slugs are suppose to shoot better out of a rifled bore than a smooth bore, but I"ve found that the Lyman is a better slug for rifled bores. I have some somewhat accurate loads for the LEE slugs, but they aren't any more accurate than some of the factory foster slugs I've used (as a matter of fact, some of the factory foster slugs are more accurate). I've probably duplicated the accuracy of sabot slugs with the Lyman.
I spent one Sunday afternoon shooting 160 slugs of 12 & 16 gauge persuasion, both factory and handload.....man, I needed some Ben-Gay for a few days after that!
As far as the lead goes, LEE recommends pure lead (no tin or alloy) for their slugs, and I think Lyman does the same, but I can't remember for sure. Hulls with a large internal capacity did better with the LEE, and the Lyman did well with the Remington Unibody hulls.
That's all I can remember off the top of my head.....hope it helps.