I use .338 win mag brass with a plastic cap on it. Although I shoot a smokeless Savage not sure your BP charges volume would fit in this case?

Yes, loose shot in my Pedersoli sxs 12 gauge. That way I can carry only as much shot as I expect to use -- not the whole bag.

For my .50 gauge rifle, I just keep loose unjacketed conicals at the bottom of my possibles bag. I hate dealing with patches.