For those members so inclined....
Constructed this crude protrusion gauge using an old, damaged extractor rod and center pin. Cut to desired size, then carefully cleaned up at the ends so that the rod and internal center pin are the same length. After drilling and threading, a small 4-40 screw holds the assembly in place, and acts as a "handle" when measuring in hard to reach places, like breechfaces, for example.
Slightly loosen the lock screw, press one end of the "tool" down over the exposed firing pin or nose, pushing center pin in tool out the other end. Measure resulting center pin extension with your dial caliper. More fun than buying one.....capital investment, zero.