What is the closest range to use Magnum's on Reactive targets?

[diverdon]

I have some Big Dog AR500 reactive targets. So far I have just been shooting them with a .308 (at 350 yards) but I have a .300 WM and a .338 I want to use. Does anyone know how far you have to be from a 3/8 AR500 target with magnum calibers so that you do not damage the target too quickly?

http://www.bigdogsteel.com/prrita.html

 

[DocUSMCRetired]

I would say at least 200 yards away. And that might be pushing it.