I wouldn't use smokeless.period in any Snider just not safe especially since the 24ga magtech brass is semi balloon head.@fourfive8
I'm well out of my zone with both but I had a brain snap last night and thought I would run it by you.
As you are basically using a straight sided shotgun case would it be possible to use a smokeless load with a saboted slug. This would eliminate small charges air space in the cartridge and the problem of paper patched bullets.
It is just a thought I had may be laughable but you never know.