[Crooked Creek]

Metric or English?

 

[Crooked Creek]

If you go back to the first set of photos posted by Lucky, right click on the photo, then left click on 'open image in new tab'. Go to the new tab, and you'll see a little + sign when you hover over the image. Left click while hovering and the 'zoomed in' close up will provide much more detail.
Looking at the presumed 'crack' seems to show it as a tool mark. And the marks on the breech face above the FP hole looks to me to have been made by a Dremel Tool stone...pretty clear.