This reclaimed shot idea had a short run about 1976. While on vacation in Arizona and doing some shooting at a club, the owner convinced me to try some, I bought 100 Ibs. of it. Used about 1 Ib. of it testing loads and patterning it. It doesn't pattern well, at least not out my two guns at the time. I still have all 99 Ibs. of it and use it in the shop when Iam gluing something up and need some weight for pressure. Works great for that. Other than that it's just deformed lead.
Never thought about the dirt aspect, but that is probably a very valid point. Be kind to yourself and your scores, my advice is do not waste your money on it for reloading shot shells, use the very best new shot you can afford. Nice round pellets that contain some antimony for hardness to help them stay round for aiding in good even patterns.