Gass relief hole botom of breech block.

[DonVoigt]

I have modified several breech blocks by adding the "Finn" hole; these were on mismatched shooter lugers. I'm not sure I'd modify a matching pistol; but then if you are going to shoot it why not? It is yours.

As to whether or not it is necessary- that is another can of worms. With modern ammo, correct headspace, and correct striker nose shape, condition, and protrusion- punctured primers are not frequent.

That said, I have fired .30 luger Fiocchi ammo with apparently very thin primer metal that punctured frequently.

The block is not hard, but I did use a carbide drill as that was what I had handy.

the size of the hole is about 3/32 to 1/8", it is not critical, but should be located just at the front of the striker bore, it is a vent. The hole is perpendicular to the bore.