Metalhed, I'd think that when the first incindiary round impacts, that your RO would have the shooter pulled off the line and banned quickly enough. Right after the full cease-fire and general everyone-run-down-and-stomp-out-the-fire drill.

If they are also scratching off the paint from the rounds, ban 'em too.

Seems to me not to be rocket science, you can't stop everything before it happens. You can't really inspect every pocket or box for every round in advance. Tell the shooters that its a "strict liability offense". Ie., no excuses. Paint or no paint, an incindiary goes downrange, they are banned permanently. Make it their problem.