At 200, you might have some slight denting. I shot my 3/8" AR500 plate at 300 with my .300RUM and 210 HVLD/215 Hybrids @ 3100, and have a slight dent. But mine was not at 30 degree angle.
If your speaking of 1/4" AR400, and using a .300 RUM, even at 30 degrees I would go 300 yards if possible. If not possible go ahead and try 200 yards, the proof will be on the plate.