If you can find some #10 try that. It will give you a higher pellet count in the center of your pattern. If not I would go #9. I don't have a 410 but have been thinking about getting one of the tristar's in bottomland. From what I've read about the guys that handload 410 in tss. They mostly use #10. And #9 with 20ga and larger guns. I do handload my own 12ga #9 TSS now.