Inertia Firing Pin & Pierced Primers

[243winxb]

2 Questions- Can an inertia firing pin produce a pierced primer? The 1911 has an inertia type pin. It would seem impossible to pierce a primer unless the primer cup was thin & defective. My thinking is the force of the pin striking the primer is the same, even if the primer is seated to high in the primer pocket. Would the primer have to be defective? If the hammer spring was extra power with an extra heavy pin, then i could see it happening. What do you think? Thank you.

 

[Fleet]

If the tip of the firing pin isn't shaped correctly, sure.

 

[243winxb]

oops, seems the AR15 in not an Inertia Firing Pin. Thats 1 reason , a bad tip.

 

[res45]

243winxb I don't shoot an AR but I do reload for several SKS rifles for different countries of origin all which have free floating firing pin. For these type rifle with free floating pins certain types of primer are not recommended.

Pierced primers can come form several thing,to much firing pin protrusion if it's adjustable,bad firing pin tip or raised ridge around the firing pin hole or in most cases using the wrong primer for these type firearms especially those that are high pressure loads.

Although primer cup thickness may be the same,the cups are not always made from the same material which can affect cup hardness and how it resist the inertia from the free floating firing pin strike as well as the pressure the particular cartridge creates. All my rifles that have the free floating firing pins use LR primers for those I use CCI #34,Winchester LR and Wolf LR or LRM primers and have never had an issue with pierced or blown primer in my 30 years of reloading. I don't recall the AR-15 having a firing pin spring now the AR-10 might.


A good article on Primers.
http://www.sksboards.com/smf/index.php?topic=56422.0

 

[Steve C]

Can an inertia firing pin produce a pierced primer?

The only time I have had pierced primers is with magnum loads that went beyond the upper pressure limit. If a primer is set high it usually will not go off as it needs to be sit firmly to the bottom of the pocket to get proper ignition. Generally th first hit by the firing pin will push it into the bottom of the pocket and if hit a second time the round will go off. I suppose if someone was to grind the firing pin tip to a sharp point it could cause primer piercing or a pin that was excessively long..

Would the primer have to be defective? If the hammer spring was extra power with an extra heavy pin, then i could see it happening.

Any time you change factory components to aftermarket out of spec parts you can get all kind of unusual results. I have seen one primer in 35 years that fizzled and failed to fire the round when the cup face cracked open and the flame excaped to the rear. This was a factory primed .357 mag case.

 

[68wj]

Excessive pressure, bad FP, oversized FP hole, bad primers: these are your main culprits (maybe even in that order). The type of firing pin system is not as important.

 

[fguffey]

Pierced primers is about balance, the yin and yang etc.. I have magic firing pins unlike all the firing pins in all other guns my firing pins crush the primer before the bullet, case and powder know their little buddy (the primer) has been crushed.

The boring story starts with diameter squared x .7854 diameter/firing pin etc. the short story version says all the shooter, reloader, smith needs to know is a pierced primer is caused by pressure, if the firing pin spring pressure is lower than the pressure inside the case/primer the pressure pushes the firing pin back, and then! a hole appears? in the primer. With more spring pressure the primer, after being crushed, forms to the shape of the firing pin, it is during this time we inter the TLZ, flat primers, primers with craters etc..

F. Guffey

 

[Slamfire]

If the stress exceeds the ultimate of the material, and the strain exceeds the elastic limits, heck yes you can get pierced primers.

Firing pin hole size and firing pin shape, along with primer material, hardness, and combustion pressure, would all need to be evaluated in the proper design of a firearm.

As for 1911 autopistols, that is a very low pressure cartridge. If you are piercing primers in one of those it is highly likely you are going to have function issues. And frame peening.

 

[243winxb]

I have never pierced a 45 acp primer in a 1911 type. My thinking is that there is only so much force contained in the firing pin. The hammer is no longer in contact with the pin when contact is made with the primer.

 

[fguffey]

I do not believe the firing pin has nothing to do after striking the primer on a 1911 or M1, I believe the firing pin is forced to stay engaged with the primer, as indicated above, If the firing pin does not stay engages the dimple/dent in the primer will flatten and the primer will not form to the firing pin. There is nothing I can do about the design and function, it is not ever necessary or required I understand why, but, ME? I suspect it has everything to do with the speed of the slide/bolt moving to the rear, the firing pin has no choice, it is pinned to the front of the slide and remain engaged until the case is ejected, and then the slide/bolt changes direction pinning the firing pin to the rear. What ever happens the firing pin is mechanically operated, mechanically anything is slower then expanding gases.

gasses.http://www.youtube.com/watch?v=XAES5SXUwVU

F. Guffey