For the life of me, I couldn't find a thread on this even though I've read several in the past...so maybe it got eaten by Kerberos or something.
Simple proposal - custom ammunition types made using the appropriate tools and skills. You want vanilla ammo - no big deal. Shop wherever. You want that custom good stuff that can potentially bypass armor, drop fleshies, or maybe not kill that bastard you're trying to abduct - talk to a specialist.