Rimfire Firing Pin

[Johnm1]

I posted about this firearm previously in the thread titled "Help Me Design a Spring"

https://www.thehighroad.org/index.php?threads/help-me-design-a-spring.896840/

One of the issues when I bought it was a broken firing pin. There were a myriad of other issues that were addressed but the firing pin remained broken. Previously I had only made the gun go bang once and I'm pretty sure that particular cartridge wasn't all the way in its chamber. Here is a picture of what I started with.



I have tried over the last few months to find a suitable replacement but no matter how similar these guns look there are usually small differences inside. I've spent way too much guessing and buying parts that don't fit/work. I decided to just replace the firing pin.

First I ground off the remaining portion of the old firing pin flat.



I Drilled a hole for a 6 x 32 screw and tapped it. There is no fear about damaging the hardness of the hammer. The only way I could tell the drill bit was biting into the face of the hammer was by the sound it made. I couldn't feel the drill bit engage the steel.



Now to fit/file to shape



Here is the finished piece





The no. 6 screw was almost as thick as the old firing pin was tall. Unfortunately I estimated the angle for the hole incorrectly and had to utilize part of the screw head to reliably fire the priming compound. It doesn't look as good as I'd hoped for. But it is functional.

Here is a test function video.

https://photos.app.goo.gl/Tfezo4bkcr9NWTSHA

I have some clean up to do and I may be able to minimize the 'hook' on the bottom. Right now the firing pin is a tad long and as such the hammer doesn't move all the way forward when it strikes the cartridge. As the firing pin moves forward the bottom of the firing pin comes further down. I'll do that after I've run a full test fire on it in its current condition.

 

[Slamfire]

It so good to see the ingenuity of individuals in fixing old firearms and making them operational again. So thanks for the post and pictures, maybe it will help someone.

I am going to claim that the reason you could not feel the drill bit engaging the hammer, is due to the primitive steels, if not wrought iron used in vintage firearms. From every metallurgical analysis I have seen, old firearms were made of plain carbon steels high in residuals that the primitive foundry technology of the day could not remove from the ladle, and thusly, the material properties are vastly inferior to the "same" steel today. I am going to claim the cheapest standard grade Chinese bolts at the hardware store are made of better quality steels than the steels of the 19th century, up to the first decades of the 20th. And, few early firearms were heat treated. At best, a case was created on the outside of the part, to induce wear hardness.

 

[Johnm1]

Firing pin strike is good. It could possibly get a little smaller and still fire the cartridge. For now the pin is just screwed in place. Once the final fit is done I'll either solder it in place or use some lock tight.

 

[Johnm1]

A couple more pictures

The pin


In the fired position.

 

[wiscoaster]

Nice work!! I'll bet the gun was pretty happy to be shootable once again.

 

[Johnm1]

maybe it will help someone.

Considering I own 4 of these and that is probably a measurable percentage of the total number in firing condition I’m not sure if this knowledge could be useful for more than a handful of people.

 

[FROGO207]

You just might give another the idea of how to fix their firing pin on another type of firearm. The sharing of the thought process to get something done is sometimes more important than the actual repair of said item. If someone made it originally then it can be duplicated by a talented enough person. Thinking outside the box gives you bonus points.

 

[AlexS1]

You have come up with a good solution, it is obvious to the mechanics. The hammer itself looks very worn. It would be interesting to know its hardness.

 

[MifflinKid]

My hat is off to salute you. Good job.

 

[Johnm1]

You have come up with a good solution, it is obvious to the mechanics. The hammer itself looks very worn. It would be interesting to know its hardness.

I would like to know the hardness too. But I'm just a 'Tinkerer' and don't have the proper tools/instruments to determine the hardness of the hammer. Best guess is this one was built in the 1880's, so it falls into that category of 'not modern' steel but probably (I said probably) not iron. It was very soft though. I drilled the hole with my drill press and I swear I couldn't feel the resistance of the steel being drilled out. I knew I was drilling steel by the sound it made.

I wonder if there couldn't be a way to calibrate a center punch type of tool that could give us hobbyists a way to get a general idea of hardness of materials. Of course we'd need an accurate way to measure the dimple. And that might be as expensive as the tool.

 

[NIGHTLORD40K]

Bravo, sir!

I once replace the broken FP on a Armi Jager AR22 with a (slightly) modified hardened industrial nail. Cut to length, beveled the tip, squared the head and presto! Worked perfectly and took about 10 minutes.

 

[AlexS1]

don't have the proper tools/instruments to determine the hardness of the hammer.

I also wanted to purchase a special tool, but it has a high price for me.
China produces hardness testers, the price is $200, but I don’t know how accurate they are.
I use the HRC scale, and I'm already used to determining the hardness "by eye". The simplest file, a file, has a hardness of about 70HRC, it does not scratch well on steel with a hardening of more than 40HRC the harder the steel, the more it slides without harm to it. Even harder 60HRC steels can already scratch glass, I check the hardness with a knife, scratching with a bottle.
It is difficult to define steel softer than 10 HRC, we call it "clay" and use it on non-critical parts. The easiest way to check steel is to heat it to a yellow color and dip it in water, if the file stops scratching it, then something can come out of this steel.