One would think a gun smith with having a surface grinder would like such a fixture..They can be used to to grind a form/Shape in a part and with using stop travel can make a form to a short arc..I don't have a grind all but have a home made version..It can come in handy.
Yes one has to fashion different holders, A round stock, perhaps 3/4 dia. 1 1/2 long , then a flat going straight for 2" makes a great clamp-on swing holder for a Grindal.