I have an M6 in 410-22 Hornet that I have tested pretty extensively. The 1/5 oz slugs from Win and Rem are very frangible. The 1/4 oz Federal is not great but does better. It also shoots well from a full choke. None of these penetrate really well on wet newsprint but the Federal is the best by a fair margin. Not only are they really light for caliber but the darn things are soft and expand.
I have seen tests of a Brenneke slug which is much tougher and penetrates better than these Forster slugs.
I am not a huge fan as I would choose the 22 Hornet on deer over the .410 barrel. In a survivalo situation I'd do it but not otherwise.
