Actually it wasn't just a blank that killed brandon lee iirc. It was the combination of a squib, and a full powder charge blank. Basically they had one scene that called for a camera angle head on to a revolver and needed the chambers to look like they had live rounds in them. They removed the powder but not the primers from some live rounds then reseated the bullets. At some point the gun was fired with one of these squibs and the bullet lodged in the barrel. Later on they were shooting a scene where they wanted the full muzzle flash of the gun so they loaded blanks with full powder charge, not realizing that the bullet from the squib was still sitting in the barrel of the gun.