I am looking to reload a few slugs for the dispatch of deer involved in road traffic accidents. Normally I use a 410 with 7 shot at very short range (1 yard) if the deer is immobile, but I would like a few slugs available if the deer is still on its feet.

I am looking for load data for the Magtech brass cases.

Thanks

410 slugs are nearly worthless for any application. They would not even exit an armadillo that I shot.
The Magtech cases are much thinner than plastic shot shell hulls and would require different wadding which I suspect you would have to make your self.
I believe there is a company that makes a load with 3 stacked buckshot that would be more lethal than the slug.