Breech Block Failure 1916/1920 Erfurt

mrerick · 01-30-2021, 10:14 AM

Is that pitting corrosion around the axle pin engagement hole? Also some galling?

That would indicate moisture got inside the breech block and toggle train. Corrosion could generally weaken the entire block, as well as retard unlock and cycling by resisting rotation around the axle pin.

While the firing pin hole looks considerably enlarged (more possible evidence of corrosion inside the block), if there were no pierced primers the only path possible for high pressure exhaust gases is around the case, past the oblation ring and back into the face of the breech block before it unlocks and extracts.

That would imply that the cartridge might not be against the chamber case stop ring. Is the interior of the chamber pitted? Is there forward / rearward play in the toggle train?

Would resistance caused by friction and pitting at the breech block axle delay extraction enough to allow the blowback around the case into the breech block?

The "go" and "nogo" headspace gauges are useful when cutting a barrel's chamber, but you need a "field" gauge to verify that you don't have excessive headspace.

01-30-2021, 10:14 AM	#29
mrerick Super Moderator - Patron LugerForum Life Patron Join Date: Dec 2009 Location: Eastern North Carolina, USA Posts: 3,920 Thanks: 1,377 Thanked 3,135 Times in 1,518 Posts	Is that pitting corrosion around the axle pin engagement hole? Also some galling? That would indicate moisture got inside the breech block and toggle train. Corrosion could generally weaken the entire block, as well as retard unlock and cycling by resisting rotation around the axle pin. While the firing pin hole looks considerably enlarged (more possible evidence of corrosion inside the block), if there were no pierced primers the only path possible for high pressure exhaust gases is around the case, past the oblation ring and back into the face of the breech block before it unlocks and extracts. That would imply that the cartridge might not be against the chamber case stop ring. Is the interior of the chamber pitted? Is there forward / rearward play in the toggle train? Would resistance caused by friction and pitting at the breech block axle delay extraction enough to allow the blowback around the case into the breech block? The "go" and "nogo" headspace gauges are useful when cutting a barrel's chamber, but you need a "field" gauge to verify that you don't have excessive headspace. __________________ Igitur si vis pacem, para bellum - - Therefore if you want peace, prepare for war.