Shovel: Catching up on the conversation. Yes...using gas Ballistics Products gas seals and mylar sheet(which you indicate you have), should work fine. I have used BP gas seals with a variety of loads, without issue.
Your AA-12 wads(Or their Claybuster equivalent) are a versatile choice, particularly for 1 1/8-oz shot payloads. I have no idea how many of either I've loaded over the years. As others suggest though, a wad with a larger cup capacity. Or, cutting off the petals and using mylar to contain the shot, is another option. In your case, since you're roll-crimping, that may work out as the best approach..
Have mentioned this before, but worth repeating: Though your tapered AA wads can accept slugs, a straight-walled wad will load easier in your Challenger hulls(Have loaded plenty of these, too. Good hulls). Of course, cutting off the petals and using the base only of your AA wads, forms a good gas seal. Plus, eliminates any issues with getting the slug to seat firmly onto the base of the wad. This method will not affect performance, in any way.
Then, just as when loading black powder shot shells, adjust stack height...if necessary, depending on powder volume.... with either hard fiber, cork or card wads, for a perfect roll crimp. Since you already have a punch, you're well on your way.
The Lee Drive Key slug, in either 7/8 or 1-oz version, are solid performers. I load the 1-oz version.. May be worth a look.
Al
