OK guys, I thought I'd drag this thread up from the dead.
Got those targets made up and have shot them on 3 different shooting sessions now.
I set them up so they were at an approximate 20 degree angle toward the ground, at distances of 70-130 yards.
Up to this point, I've shot them with 7.62x39mm, 7.62x54R, 308, and 223, to name the significant bullets.
On the first time out, I found out that the 1"x1" angle I used to support the targets was inadequate, to say the least, when I missed and hit the support structures. I immediately brought the targets back to the shop and re-vamped them with 1/2" flat steel.
Other than that, the targets work great. I have yet to find a caliber that will dent the 5/8" thick bush-hog blades. The flat steel doesn't fair as well, but I'd say they'll last for at least 30 'misses', at least.
Up to this point, ricochets have been non-existant at the yardages I've used them at. I actually find the combloc bullet shrapnel(sp?) lying on the ground all around the targets. As I improve, the distance to the targets will only get greater, so I think ricochets can be ruled out as a problem at 70+ yards.
Just thought I'd share.