Shot Drop Miseries

[William Machauer]

I've tried powdered chalk, no joy.
What I have found is powdered graphite as others have said but I put shot into my RCBS tumbler with the graphite and let it do the work.
I only use magnum shot, I don't experience barrel leading.
I've been trying to use up some oxidized shot and I soak that in white vinegar then tumble that in graphite. Still not perfect but it helps.
Also I use a single stage MEC 700 I converted for 410. After I seat the wad I lift up the handle some before dropping the shot, I keep a dowel handy to rap on the drop tube.