What causes this wear on a firing pin?

[Gdub]

Picture is a Large Frame Extreme Firing pin. Result is FPB does not work if you press hard on the back of the firing pin when it is engaged with the hammer fully cocked.

What needs done so this does not happen again?

Thanks,

Edited March 23, 2016 by Gdub

[Nealio]

On a stock gun, the firing pin actually hits the FPB when you fire it. I've detailed how to "tune" the FPB so that it does not contact the firing pin, but there are other factors that can cause this.

If you shorten the sear engagement leg too much the trigger bar can slip off the sear after the hammer is released. This can cause the FPB to drop back into place prematurely and catch on the firing pin, and also cause your sear to hit the 1/2 cock hooks.

Or you've changed the hammer and/or sear and its not taking the FPB out of the way enough, so you've worn the edges off.

[BeerBaron]

It was almost certainly caused by it hitting the fpb during firing. Fpb needs some fitting (along with new pin) so it won't interfere.

[johnbu]

My google-fu is weak and the search results aren't showing what is done to fit the new fpb.

Nealio, would you be so kind as to restate the procedure?

Mine would not allow the FP to go forward with the hammer cocked and holding the hammer and trigger back while checking didn't feel any drag....yet there was still interference marking on the pin and wear on the block after lots of da dry fire.

[Gdub]

My google-fu is weak and the search results aren't showing what is done to fit the new fpb.

Nealio, would you be so kind as to restate the procedure?

Mine would not allow the FP to go forward with the hammer cocked and holding the hammer and trigger back while checking didn't feel any drag....yet there was still interference marking on the pin and wear on the block after lots of da dry fire.

Thanks to everyone for the input. Mealie, could you repost you or send a link to the proper fitting of the FPB?

Thanks,

[Nealio]

First I take the FPB out, and then adjust the over travel for the trigger/sear so there is not too much overtravel, but NO contact between sear and 1/2 cock hooks when the trigger is pulled and the hammer is lowered by hand. Then put the FBP back in.

To fit the FPB:

Cock the hammer, then use a punch to try and push the firing pin in to make sure it engages. Then hold the hammer down and pull the trigger all the way back. Push the firing pin in again. At first you can feel it hitting/hooking on the FPB (sometimes a lot, sometimes a little). Take the FPB out again and stone down the "tooth" part (ie the part that everyone keeps showing as rounded off) just a tiny bit. Make sure that stays square and not rounded or beveled at all. Put the FPB back in and repeat until the contact feels like its just rubbing and doesn't hinder the movement of firing pin. From this point I take like a thousandth more off, but you can leave it this way. Just be careful that you don't take too much off, or then you need a new FPB.

[johnbu]

First I take the FPB out, and then adjust the over travel for the trigger/sear so there is not too much overtravel, but NO contact between sear and 1/2 cock hooks when the trigger is pulled and the hammer is lowered by hand. Then put the FBP back in.

To fit the FPB:

Cock the hammer, then use a punch to try and push the firing pin in to make sure it engages. Then hold the hammer down and pull the trigger all the way back. Push the firing pin in again. At first you can feel it hitting/hooking on the FPB (sometimes a lot, sometimes a little). Take the FPB out again and stone down the "tooth" part (ie the part that everyone keeps showing as rounded off) just a tiny bit. Make sure that stays square and not rounded or beveled at all. Put the FPB back in and repeat until the contact feels like its just rubbing and doesn't hinder the movement of firing pin. From this point I take like a thousandth more off, but you can leave it this way. Just be careful that you don't take too much off, or then you need a new FPB.

That's what I "thought" I was doing, yet there is evidently some contact as it rounded off the tooth. Can the timing of the hammer release to FPB getting pushed down be checked / adjusted? Or did it just need a touch more?

[Nealio]

If your trigger bar slips off the sear engagement leg (which can happen if you shorten it too much) the FPB will be released and can nip at the firing pin.

Or the timing when shooting DA could also be a factor. If you change the hammer, disconnector, or sear that could change the timing of this, so that could be an issue as well.

I would slowly pull the trigger back in DA until you find the release point, then hold the hammer down and see if the FPB is out of the way enough.

[johnbu]

If your trigger bar slips off the sear engagement leg (which can happen if you shorten it too much) the FPB will be released and can nip at the firing pin.

Or the timing when shooting DA could also be a factor. If you change the hammer, disconnector, or sear that could change the timing of this, so that could be an issue as well.

I would slowly pull the trigger back in DA until you find the release point, then hold the hammer down and see if the FPB is out of the way enough.

Don't think it's the "sear engagement leg"...not even sure which it is!

The sear and hammer are extreme, the disco is a T3. So, im "assuming" that might be it. Will do the test outlined and see.