A lot of Norton abrasive sheets just say "Aluminum Oxide". Fused versions in grinding wheels are called alundum. Aluminum oxide (aka alumina) abrasive is a lot like garnet in that the grains are rounder and less sharp than silicone carbide or boron carbide or diamond. It makes a smoother surface, generally speaking, but cuts more slowly.
All this begs the question about whether oxide on the surface of a screen, which is smooth rather than granular, and porous rather than fused into solid grains is actually going to cut or just polish a little. I haven't done the aluminum screen experiment, but suspect polishing is about the worst that would happen unless you shot aluminum bullets all the time.
DarthNul,
sounds like you got it done. Next time get it wet with Kroil and leave that sit overnight and I think you'll find the lead pops off the surface even more easily. If you want to use lead bullets regularly, consider light firelapping to polish the bore surface, as this cuts down on lead adhesion.
I've also had good luck with Sharpshoot'R NO-LEAD. Over a period of an hour it reacts with the lead to form a black crumbly compound that patches right out.
Avoid the vinegar and peroxide trick unless your gun is stainless. That mix will take bluing off.