Serious dry firing is an important aid in learning to shoot well and in diagnosing problems when you suddenly stop shooting well. From the broken firing pin thread it looks like firing pins really do occasionally break, even in modern guns. It may be pretty rare but still a concern.
The obvious solution is snap caps which are supposed bring the firing pin to a gradual stop and prevent the sudden tensile stress on the firing pin when otherwise it suddenly hits the end of travel. My question is where can you buy snap caps that will actually do that?
The snap caps I have are of a transparent plastic and you can see the spring that resists the blow. It doesn't take too much heavy thinking know that the spring could be either too weak to slow down the firing pin much before it fetches up suddenly -- or it could be too strong and cause the pin stop suddenly although by putting the tip of the firing pin in compressive stress instead of tensile.
A snap cap could be made by using a case with a compressible elastic material in the primer pocket. But these could also be too compressible or not enough.
Of course it can be argued that cushioning at all of the firing pin is a step in the right direction -- but how much?
Is there any known testing on any snap cap that shows that they do their job well?