Sounds like he is talking bullets, though he refers to them as slugs.... And making .458 bullets out of .40 S&W brass ? I would think is a bit strange.
Edit: Actually found an article on this, they are using ,45 ACP cases to make .458 SOCOM bullets..... Whodathunk....
Hmm, I missed that one... Interesting and good to know but thankfully I'm set for a bit.
Also forgot to look for the Hornady 300GR bulk bullets but they're out there too. OP, I think there are some components for sale over on the 458S Forum.