Hi, all my AR500 steel targets hang down straight where the lead splats out 360 degrees. Occasionally I find a 2" diameter lead foil at the bottom of the target from slow large pure lead projectiles. Even if I could recover the projectile parts, the lead would be dirty and require work to reuse. Also, since I shoot both hard and soft lead at the same targets, the recovered lead wouldn't be soft. Pure lead for the cost of less than $2/lb is my preferred path for casting projectiles for muzzleloaders.
The AR500 Cowboy target is mounted ready for shooting with my 1853 Enfield today. I had cast 0.575" minies, but will try using newly cast 0.578" minies. The original 1853 Enfield had a bore of 0.577" where the 0.575" minie ball is ideal. However, the Chiappa 1853 Enfield and 1861 Springfield have a bore of 0.58" where the 0.578" minie may give better accuracy.
Edit: Shot the hell out of my new AR500 steel Cowboy using the Traditions 1853 Enfield using the 0.578 minie and 40gr of Black Mz. The Cowboy isn't a virgin anymore. The rifle shoots ~8" high, but groups <1" @ 25yds.
BTW, Traditions has a great deal on a 2nd 1853 Enfield, $705:
https://www.traditionsfirearms.com/product/1853-enfield-musket-rifle-.58-caliber-rifled-specialRegards,
Richard