It was some 6" paddle kits on Amazon rated for rimfire I think it is the same or similar to a36

I shoot some steel and 3/16 AR400 works for as high as 380 ACP. Can’t shoot a 9 mm at that or your risk dimpling the target. You should be fine with 1/4 inch AR400. 

I’ve never heard of AR200 being used on steel targets.

I want to build a dualing tree in the future, but I am wondering on what thickness to go with all my current gongs are 3/8 but was thinking 1/4 for the dualing tree. I plan to stick with ar500 but what are people's opinions on ar400 and ar200.

Dueling tree what thickness for the paddles?