I've just seen your post on another thread. You're using range scrap and just going going to replace the shot of a factory cartridge with the slugs you've cast?

Do not. You are posing a massive risk to yourself and anyone around you.

Buy a shotgun loading manual. A proper one such as Lyman. Then get too it. Slug shooting can be great fun and casting and loading even more so. But your current approach is dangerous.