How easy or difficult is it to machine new parts for broken machine guns in general? I imagine it depends on the part, but is there any rule of thumb?
I bold'd it for you because you answered your own question. I've had to have a few parts made here and there over the years, all depends on the complexity of the part and the skills/tools of the machinist...it can get pricey, so I (and I'd say most guys with MG's) buy spares when we find them whether we need them or not...