The only spares that I will always have is the bolt return spring - it is so small that I tend to lose it. Since I am an inveterate tinkerer, I am inside my working guns pretty often. I know that there are some that don't agree with that, and in principal, I agree with their perspective when it comes to your collectible guns.

I assume that you are asking with respect to a working gun, which I treat differently than a gun that is more of a collection piece.

I have never had a hammer nose break, but I have heard of it. Now that it is mentioned in this thread, I think that a nose and rivet will be in my toolbox from now on.