Many guns can be damaged by dry firing, but not an A H Fox.
In the article "Why Should I Buy A Fox Gun?", in Volume 11, issue 1 of DGJ years ago, Tom Kidd wrote (in quoting Fox literature), that it will in no way damage a Fox gun to dry fire it, because of the way the hammer is designed and the way it meets the rear of the standing breech. As I recall it was described as having a substantial boss for the hammer to meet, not allowing the rear of the firing pin itself to ever contact the steel around the firing pin hole, preventing any possibility of "mushrooming" the steel around the hole as is seen on so many other old doubles.
I don’t see how that’s possible. I just completely stripped and cleaned two Fox doubles and nothing inside of there said to
me that dry firing would be a good idea. The tumbler/hammers on a Fox are massive, very similar to & about the same as a Greener FP tumbler/hammer, but I don’t see anything in the Fox action that would prevent the hammer assembly from smacking the front of the firing pin hole when loosed. I certainly wouldn’t recommend it.
Kind of off topic, but the Fox is kind of a [censored - come on man!] to disassemble and reassemble. That clevis pin/screw is a real piece of work(I guess Fox never thought these guns should be fully disassembled for cleaning or repair!!). Why they thought that should be peened over I’ll never know. Second thing is the mainspring plunger and yoke doo-hickey. What an idea. Pain the butt to put back together.
On the broken firing pin question….what make of gun are you talking about? Something with bushed or separate strikers/pins or a gun with integral pins with the tumblers/hammers?
Using a an old drill bit to make a firing pin. Sure it could be done. Gotta think about the hardness of hss, carbide, etc. and how it’ll affect that tumbler/hammer. If it’s too hard, it might break prematurely or it’ll start to peen the tumbler/hammer or worse yet, crack it. Probably best to use mild steel rod, turn a new pin and then properly harden and temper it.