Find a piece of old steel and rough it up in two different areas with some sandpaper. Then pull the bullet with pliers, and dump the powder from a round. Put on some protective eye-wear and leather gloves. Put the empty shell in some vise-grips. Take a punch and hammer, and detonate the primer while pointing the empty shell at the Area 1 of the metal you roughed up. Use Area 2 as a comparision (don't let primer spray get on this area). Let the metal sit for a week in your garage and see if it developes rust. If no rust appears, the round is likely non-corrosive. If rust appears on area 1 and not on area 2, then the round is corrosive.
Note: Be careful because the primer may eject from the round when you detonate it. When I do this I wear a full-face motorcycle helmet, jacket and leather gloves.