RHB:
They look to be of the same design as the RC4, but the alloy must be considerably better (and thicker!) if you can shoot them into a clay-bank and retrieve them in one piece. The fired recoveries look great to me! I would have been happy with the RC4s if they could have achieved that.

Nevertheless, the true test is to whack them into the shoulder of a full-grown wild boar and see what happens! Have you taken the Mirage slugs into the hunting field? We would love to hear your results.

Whatever the outome, you would still be better off than those two guys with hay-forks!

Original Brennekes are true solids with riveted base-wad (no hollow base), although there are a few modern variations around these days which may be slightly different. Here's a pic of two recovered from buffalo, not mine (found on the web), but you get the idea: