I recently bought a 3/8" ar500 steel target specifically for shooting surplus steel core 7.62x54 @100-150yds. From my experience the only way that you even significantly cratered a 1/2" plate @200yds is if the range is lying to you and it is NOT ar500 steel or you accidentally bought actual armor piercing ammo and not the regular mild steel core com-bloc surplus.
I have two 3/8ths inch steel AR 500 silhouettes that I have shot with many hundreds of rounds of 7.62X54 Silver Tipped steel cored ammo and there is no visible damage to the plates at all.
This is the ammo I'm using:
If this is the ammo the OP's using, it would not pierce half inch AR500 at 200 yards,