How do you properly measure the throw of a breechloader hammer? Is it from the center of the hammer face to the center of the tumbler hole? Is the offset measured from the flat which is against the lock to the center of the hammer face?
Thanks,
CHAZ

Measure from the center of the hammer pin [axel ?] to the center of the firing pin. For offset, you are generally right, but keep in mind that the hammer does not fit flush on the "flat " as you call it. There is a bit of a gap that must be taken into consideration.

If you are talking hammer gun then it would be from the fully cocked position to the bottom of the travel taking into consideration the re bound . If talking hammerless then it will depend on the gun .
If you mean where should the hammer hit the striker on a hammer gun then as cclose to centers as possible .

Seem to remember Dixie Arms ctalogue used to carry all this type of information, are they still around?