Gass relief hole botom of breech block.

[Dwight Gruber]

Originally Posted by HisSoldier

While searching info on fluted firing pins here I learned that it was not done to prevent damage from pierced primers, but I did find a mention of Finnish P-08's that had a relief hole under the breech block, likely from the front of the cylindrical bore for the firing pin, for that very reason.

I don't know if it's statistically a likely event but it sure sounds like it would be a costly one if it damaged the rear of the retaining lock area...

The reason for the firing pin flutes, according to the patent involved, is to collect burned powder residue and reduce the possibility of fouling the firing striker. The assumption that they reduce the possibility of damage in the event of a pierced primer is the purest fantasy of undocumented "conventional wisdom," as there is no place for the high gas pressure to go within the breechblock body whether the firing pin is fluted or not. I have many friends on this board who will take umbridge and serious exception to this bald statement.

The most common damage from a pierced primer is the firing pin being forced backwards hard enough to break away the back of the retaining slot for the firing pin retainer, effectively destroying the breechblock.

I have had correspondence with a Finnish member of this board--If I remember correctly it was Juha--who agreed with the speculation that the Finns drilled the breechblock gas relief hole because the extraordinarily cold conditions there caused the metal of the primers to become brittle with the cold.

--Dwight