That was my view during the design as well; I just didn't see the need for the extra expense of tool steel for the arms. They are pretty short, and unless you get carried away with the press, I made them beefy enough that you won't be able to bend them. Two of the three arms have a hardened drill rod insert; this is the part that contacts the rivet and it is unlikely to mushroom out unless you plan to make dozens of rifles.
I did look at tool steel parts, but the steel price would drive the price of the jig up another $30-50, not including heat treatment, and it would add quite a bit to production time since I can't do the treatment myself.
Originally Posted by robpiat