I'd venture to say that most all mil-surp rounds will have some steel in them. Thus any ammunition made with surplus bullets would have steel. With that being said all Ball, Tracer, AP, API, APIT ammunition will most likely be at the very least copper clad steel jackets, with the possible acception going to ball ammo, which could possibly be plain copper jackets if manufactured commercially. All AP, API, APIT rounds will have a hardened steel core, thus the AP (armor piercing).
The only one I'm not familiar with is the Match bullets. If they are mil-surp then I'd say maybe-probably steel jackets, but if Commercially made they will have no steel content whatsoever. With the exception going to commercially made match bullets turned out of leaded steel, but these would be easy to spot.
The common theme here is that if the bullets were made for military use then you can pretty much expect steel jackets or steel core.
As far as 'true' factory loads go there are several companies that manufacture, not remanufacture' 50BMG ammo using commercial bullets, usually either match or fmj bullets.
