Hi Peter and welcome. A 410 is plenty effective with the least amount of recoil. Recommended self-defense loads are here: budsgunshop.com/product_info.php/products_id/86344/sellier+%26+bellot+shotgun+buckshot+.410+ga+2.5+000buck+25rd+box --------------------------------------- budsgunshop.com/product_info.php/products_id/84263/hornady+critical+defense+.410+ga+fxt+slug+with+flex+tip+20rd+box -------------- Cheers, stay safe and enjoy!

Listen, I wouldn't want to get hit by a .410 cartridge but, I'd still go with a 20 gauge personally. With a .410 they are very light on the load they hold. With a 20 gauge shell you're getting closer to what a 12g shell holds.
In a 20g you'll get More pellets in a buck shot and better pennetration for home defense use if necessary.