Which blast media?

Hey all,

I use 60 grit aluminum oxide in my gunsmith/machine shop blast cabinet. Lately I have been using it on some front end parts and it just isn't aggressive enough for rusty scaly surfaces.

What do you recommend? I won't use any silica indoors and "black beauty" isn't much good either for a system that recycles the media. It just breaks down too quick in my experience.

What do you like?

Thanks

CE