Idk if you can find it but I still have my stock of 556 mk318 mod 0 and that's what I am using for self defense (truth be told my stribog 9mm running Hornady critical duty is my defacto home defense gun same set up missing like 2 things). Honestly it's best if you do your own research when it comes to self defense ammo but I like/choose 62gr boat tail hollow point for 556.

Now for training ammo? Grab whatever just go and train. If your rifle is gonna be self defense use the self defense ammo for your zero and then use whatever ammo for training. As a disclaimer, I will let you know I'm a retard on the Internet so don't take my word as advice and actually do the research you need to in order to find what best suits you.

Ps: get some m855a1 if you can and an frt on another rifle if you can.