"Over-sized" Firing Pins

[Jack Suber]

Has anyone here used an "Over-sized" firing pin like EGW offers. Not the Extended Firing pins but the one that are larger in diameter for the purpose of reducing primer flow into the firing pin hole? I am curious as to your thoughts and why you have one in your gun? Was it to control firing pin flow? How does it work.

I think the last batch of Winchester SP primers I got are significantly softer than previous batches. I started to get primer flow with my loads that I never had before. The flow is significant enough to shave material off of the primers and cause misfires. I have mic'd the base of my brass (prior to and after firing) and there has not been significant expansion. 40 cal brass which is Case-pro'd mics at .422 prior to firing. After firing, it mics at .424 - .425". Primers are flowing in both of my guns. The primers are the only thing that has changed. I have standard pins in my STIs that mic at .060" Was thinking about going to the .068 firing pins that EGW offers.

thanks.

Edited June 2, 2011 by Jack Suber

[Brazos Custom]

Standard STI firing pin should be 0.066 for 38/9/40. If you are using an STI slide that diameter will work well. Quite often the 0.068 won't work in the STI slide without being turned down. If you have a Caspian slide the 0.068 works well.

[Powder Finger]

Yes, almost all my guns have them.

Originally used them to get P9's to run as the power factor was 18,000,000,000(or something like that).

And they solve the flow problem fairly well. After that I just used them so there was one less thing to worry about.

Even if I'm not using a true oversize pin I make sure the fit is close and just go through the box of pins until I find one.

The deal with them is at the point of ignition there is no gap for the primer to flow into.

Even with an oversize pin you can get the pin drag on unlock, but I can't say that ever caused a misfire.

I don't recall any of my 1911 guns having the pin drag deal happen.

Hope that helps.

[Jack Suber]

Standard STI firing pin should be 0.066 for 38/9/40. If you are using an STI slide that diameter will work well. Quite often the 0.068 won't work in the STI slide without being turned down. If you have a Caspian slide the 0.068 works well.

Thanks for the reply, Bob. Correction to my initial post - the current firing pin mics at .066. The slide is an STI slide. I took an old firing pin and inserted it into the firing pin hole from the breech face. Then I took a permanent parker and marked the pin flush with the breech face. I mic'd the pin at the point where it was flush with the opening and it mic'd at .073". I know that isn't very precise, but it was the best I could do. Could my slides have eroded? There is no evidence of such. Should I try a .068 firing pin?

[Brazos Custom]

0.073 is pretty big for an STI slide. The only time I have seen erosiont is if the large diameter hole for the firing pin is drilled too close to the breechfaceand the material is too thin. EGW makes quite a few different diameters of firing pins and should have something to match your slide. To get a precise measurement I would see if you can find someone that has some gauge pins or maybe find a #49 drill bit which should be right at 0.072 at the shank.

[bassochist]

i use an matt mclearn firing pin, it is 0.69 in diameter (striker part)

with a standart sti firing pin i had excessive primer flow, but the m2i firing pin totally eliminated that.

[Pat Miles]

I've used M2 extended firing pins that measure .068" at the tip. They would hang up in an STI slide so I use a .070" reamer and they fit just fine now.

Pat

[Jack Suber]

Just a follow-up - The EGW .068" Firing pin fixed the problem. Wish I had realized that was the problem before the Va/Md. Oh well, live and learn. Thanks for the feedback everyone.