The Military has sold literally millions of rounds of armor piercing ammo for the .308 and .30-06 and maybe even the .223 as well.....I've not looked but it's likely that AP rounds are also available for the 8MM Mauser too.

I think you need a lot of coaching to pull off this bullet making trick and I doubt seriously that it's illegal at all.....especially if you don't try to sell them.

I'm not having any luck trying to guess what purpose you have but look for off the shelf AP bullets in 8MM. If you're unfortunate enough to find some to make them for you, I sure hope he knows what he's doing.