thomis said:
1- if the primer wasn't seated deep enough into the primer pocket, there is no way on this green earth the striker is strong enough to seat it further, especially without setting off the primer, just don't buy it.
Primers are packaged with the anvil not set against the priming compound and the anvil feet sticking below the primer cup (see close up pictures below). For proper primer ignition, the primer needs to seat deep enough for the anvil feet to hit the bottom of the primer pocket and anvil to be pushed up against the priming compound. Unmodified factory primer pocket depth varies depending on the head stamp so if a primer cup is seated slightly above flush or even flush, the anvil may not be in contact with the bottom of the primer pocket and the first firing pin/striker hit may not ignite the priming compound but rather seat the primer cup deeper, setting the anvil against the priming compound. For this situation, second primer strike will ignite the priming compound -
http://www.thehighroad.org/showthread.php?t=630512&page=2
Pictures showing different brand primer anvils with corresponding priming compound seals/caps. The color you see on the bottom of the primers is not the color of the priming compound but the color of the seals/caps.
Different brand primers showing different amount of anvil feet sticking below the primer cups. Depending on the shape, height of the anvil tip and the length of the anvil, different primers may require different amount of seating depths to properly set the anvil tip against the priming compound for ignition.
2- if the primer wasn't seated deep enough into the primer pocket, that means its closer to the striker, not farther, which would give a weak striker more chance of setting it off, assuming the cartridge doesn't move during the strike.
Priming compound ignites when the anvil compress the priming compound against the indentation of the primer cup. If the anvil tip is not set against the priming compound, indenting the primer cup will not necessarily ignite the priming compound but seat the primer cup deeper.
3- your theory of the striker setting it off the second time after the striker seats it further doesn't work because of the aforementioned reason AND the fact that I've loaded the rounds with light strikes back into the magazine over and over again and they still won't detonate.
I experienced this issue with a particular lot # of Tula small pistol primers with harder cups. The picture below shows a primer hit 3 times. To rule out weak striker spring, I seated the offending primer in a 45Auto case with small primer pocket and hammered twice with my Sig 1911. The primer was hand seated to below flush to ensure the anvil was properly set against the priming compound -
http://www.thehighroad.org/showthread.php?p=7805786#post7805786
Primer cup with 1 striker hit (as indicated by the pink intact priming compound seal, priming compound did not ignite)
Picture showing striker hit #1 and hammer strike #2 and #3 - primer did not ignite.
After thee primer hits, the primer was deprimed and showed intact pink colored priming compound seal.
Was I certain that it was hard primer cup that was the culprit for the primer failing to ignite?
To verify this concern, I fired CCI SR primer known for harder than typical primer cups and Tula SR and .223 SR primers in the same striker fired Glock used for above Tula SP primer tests and as indicated by the black fouling, they all ignited.