I've been having a blast with an old Double Barrel, shooting 50 grains of 1 F with an ounce of shot, a lubed 1/2 " fiber wad on top of the powder, and an .062 card on top of the fiber wad and also on top of the shot. I am roll crimping them on my drill-press. For what it's worth, I am cutting down 3 inch crimped cases to 2 5/8 " with a big wood drill chucked into the drill press to get rid of the star crimp and make the cases the right size for my oldie but goodie.
Anyway... after I shoot the cases are all yucked up with BP residue. I assume the residue is long term bad for the cases. I have been rinsing them out with water and a brush after decapping, and letting them air dry for a day before reloading again. It hasn't happened yet, but if the cases start looking bad, I'll just toss them and go find some more free ones in the trash can at the local range.
Does anyone clean plastic shotgun hulls after using BP in them, and how do they do it?