Firing Pin Failures....MIM!!!???

[Ultima-Ratio]

Randy said his FMFP was .500-.501, dang nice to know sizes...thanks tomcat!

I'm whipped into using throat reamers (chuckle, .501 is the reamer size I ordered for the .500s) on later Smyths and many Rugers, also gotta case harden the ejector center pins to prevent peening from heavy Alaska loads......add .500 grips to the Maggies

Bottom line folks, we all know why the Rugers are larger than Smyth counterparts right?

MIM being metal injected into a mould has inherent porosity (read weakness!) not found in forged metal..(carving the tenderloins from said dead horse..)

 

[bountyhunter]

MIM being metal injected into a mould has inherent porosity (read weakness!) not found in forged metal

No, it does not. You are confusing CAST with MIM. cast pices are significantly less dense than forged (like 60 - 70%) but MIM parts are as much as 95 - 98% as dense as forged metal.

Since MIM parts are injected into a mold, they have a possible flaw of having an air void if not done properly. That is not porousity and simply means the bozo making them did not control the consistency of the slurry.

You might want to actually read up on the MIM process. In a nutshell, a mixture of metal powder and polymer bond is forced into a mold. The "green" part is fired at a high enough temp to fuse the metal particles into solid metal. The only thing it has in common with casting is the use of a mold.

 

[Ultima-Ratio]

Bounty? Did you proof read your post?

The combination of plastic (read oil) and powdered metal (Which Metal?) is somehow as strong as forged steel?

Nonsense!

In layman's terms, Ruger vs Smyth cylinders the Smyth ALWAYS is stronger in destructive testing.

Read just add more 2400 until the cylinder blows, the Smyth always is stronger...duh.

BTW, mold is something that grows on bread among other things...the study of fungi is a wide open field btw....maybe a dozen experts worldwide.

My new Smyths tend to misfire in the cold and now break firing pins..the Rugers don't. I love my Smyths and will tinker when need be but do I have to whack an olde style hammer to fit (added weight?) plus find a forged FMFP for reliability?

I'm a 62yr olde smith that folks pay for expertise K? THIS is Alaska, critters will eat us. Care to share how YOU would prepare a new Smyth to avoid Murphys Laws?

 

[tomcatt51]

Originally posted by Ultima-Ratio:
I love my Smyths and will tinker when need be but do I have to whack an olde style hammer to fit (added weight?) plus find a forged FMFP for reliability?

The 5" PC 627's hammer is forged and is for the FMFP (pinned sear too). It would be a drop in for your 625-6. I just sold the one that came out of my 627.

FWIW I've weighed the MIM and forged parts and the MIM parts are quite a bit lighter.

I thought Ruger had gone (quite a few years ago) to injection molding (or investment castings?) for their revolver frames.

 

[bountyhunter]

Originally posted by Ultima-Ratio:
Bounty? Did you proof read your post?

The combination of plastic (read oil) and powdered metal (Which Metal?) is somehow as strong as forged steel?

Nonsense!

I'm not going to waste any more time arguing. One of my degrees is in mechanical engineering so I probably lose more knowledge on the subject of MIM when I sneeze than you seem willing to ever learn.

You can research MIM if you want to, but posting this:

The combination of plastic (read oil) and powdered metal (Which Metal?) is somehow as strong as forged steel?

shows you have no clue. The polymer binders mixed with the powdered metal is burned out during the sintering process which fuses the particles into solid metal, the final piece does not contain the binders. It is about 95% - 98% as dense as a forged part. Like I said, the internet awaits if you actually want to learn something on a subject you clearly know nothing about. The difference between a well made MIM part and a forged part is miniscule in terms of tensile strength.

 

[bountyhunter]

Originally posted by Ultima-Ratio:

My new Smyths tend to misfire in the cold

Then they either need cleaning or repair, or need to be fed decent ammo. A maintained gun with full power springs will not misfire on decent ammo.

Originally posted by Ultima-Ratio:
BTW, mold is something that grows on bread among other things

Uh huh

Originally posted by Ultima-Ratio:
I love my Smyths and will tinker when need be but do I have to whack an olde style hammer to fit (added weight?)?

So, are you now saying a HEAVIER hammer will increase strike force to solve your misfires?

That will come as a real surprise to the dozens of people who sell low mass hammers and strikers for competition use specifically to allow good strike force with low power springs. Those silly people think reduced mass hammers increase strike energy....

Originally posted by Ultima-Ratio:
Care to share how YOU would prepare a new Smyth to avoid Murphys Laws?

Are you asking how I tuned the dozen or more smiths I own and shoot in competition? That would require more time than I care to waste on this thread, but I'll guarantee you one thing: I can certainly make a new SW fire 100% reliably in any weather you can find. As for the massive plague of broken firing pins you claim: you may want to look up the definition of "anecdotal"....

The number of broken stock SW pins I have heard reported total exactly ONE: yours.

 

[bountyhunter]

Originally posted by Ultima-Ratio:
Bounty? Did you proof read your post?

mold is something that grows on bread among other things...the study of fungi is a wide open field btw....maybe a dozen experts worldwide.

OK, I think I understand: since my post contained the word "mold" and yours "mould":

Originally posted by Ultima-Ratio:

MIM being metal injected into a mould has inherent porosity

I assume you are implying that I did not spell the word correctly in referring to a "mold" used to make a piece. You are wrong again:

http://dictionary.reference.com/browse/mold

mold1 /mo?ld/ Pronunciation Key - Show Spelled Pronunciation[mohld] Pronunciation Key - Show IPA Pronunciation
–noun

1. a hollow form or matrix for giving a particular shape to something in a molten or plastic state.
2. the shape created or imparted to a thing by a mold.
3. something formed in or on a mold: a mold of jelly.
4. a frame on which something is formed or made.
5. shape or form.

As you can see from the dictionary, my use of the word "mold" is correct.

That doesn't come as a big shock to me: at last count, I had about 40 published articles in various trade magazines. I think I can handle four letter words like "mold".

 

[Ultima-Ratio]

Originally posted by bountyhunter:

Originally posted by Ultima-Ratio:
Bounty? Did you proof read your post?

mold is something that grows on bread among other things...the study of fungi is a wide open field btw....maybe a dozen experts worldwide.

OK, I think I understand: since my post contained the word "mold" and yours "mould":

Originally posted by Ultima-Ratio:

MIM being metal injected into a mould has inherent porosity

I assume you are implying that I did not spell the word correctly in referring to a "mold" used to make a piece. You are wrong again:

http://dictionary.reference.com/browse/mold

mold1 /mo?ld/ Pronunciation Key - Show Spelled Pronunciation[mohld] Pronunciation Key - Show IPA Pronunciation
–noun

1. a hollow form or matrix for giving a particular shape to something in a molten or plastic state.
2. the shape created or imparted to a thing by a mold.
3. something formed in or on a mold: a mold of jelly.
4. a frame on which something is formed or made.
5. shape or form.

As you can see from the dictionary, my use of the word "mold" is correct.

That doesn't come as a big shock to me: at last count, I had about 40 published articles in various trade magazines. I think I can handle four letter words like "mold".

Ahhhhh, I understand now! Bountyhunter is in marketing, or if I may...a ragwriter paid to sell a product. Yep, I got it.

I'm a lowly consumer/smith and Master Finisher tho I have studied some on the psychology of marketing/hyperboly...chuckle.

You ever sell anything to Industrial Finishing?

 

[mhp339]

In layman's terms, Ruger vs Smyth cylinders the Smyth ALWAYS is stronger in destructive testing.

I hope Ultima-Ratio isn't implying that Ruger cylinders are weaker than Smiths due to them being cast vs. Smiths being forged. Ruger cylinders are not and have never been cast; they're still cut from round stock just like Smiths. It's one part that's still cheaper to cut than to cast.

 

[bountyhunter]

Originally posted by Ultima-Ratio:

Ahhhhh, I understand now! Bountyhunter is in marketing, or if I may...a ragwriter paid to sell a product. Yep, I got it.

Clearly what you understand on this subject could be inscribed on the head of a pin with room left for the Gettysburg Address.

Please keep your smart mouth personal attacks to yourself in the future.

Originally posted by Ultima-Ratio:
I'm a lowly consumer/smith and Master Finisher tho I have studied some on the psychology of marketing/hyperboly...chuckle.

Too bad you never studied anything about metallurgy, sintering, or how MIM parts are actually made. The thread might not have been such a colossal waste of time.... and if you studied English, you'd know the word is "hyperbole".

Originally posted by Ultima-Ratio:In layman's terms, Ruger vs Smyth cylinders the Smyth ALWAYS is stronger in destructive testing.

What strength? Tensile strength, shear strength? Which SW cylinder, stainless or carbon steel?

Never mind, I forgot what I was asking for a moment.

 

[bountyhunter]

Originally posted by mhp339:

In layman's terms, Ruger vs Smyth cylinders the Smyth ALWAYS is stronger in destructive testing.

I hope Ultima-Ratio isn't implying that Ruger cylinders are weaker than Smiths due to them being cast

You came in very late to the thread. All the smarter posters gave up long ago bothering to answer his posts.

 

[Stophel]

Bountyhunter, thanks for the explanation of just what MIM actually is. It seems it is basically formed "dry", and then melted inside the mould (rather than poured into the mould as with normal casting). I wasn't sure just how it was done before.

Oh, and please excuse my ignorance, but just what the heck is FMFP???

 

[imashooter2]

Frame Mounted Firing Pin as opposed to the older hammer mounted pins.

 

[bountyhunter]

Originally posted by Stophel:
Bountyhunter, thanks for the explanation of just what MIM actually is. It seems it is basically formed "dry", and then melted inside the mould (rather than poured into the mould as with normal casting).

Not exactly: metal powder is mixed with polymer binders (basically glue to hold it together) and then it is force injected into the mold under pressure. The part is then taken out of the mold and is what they call a "green" part. As I understand it, the part has no strength and can be crumbled by hand since none of the metal particles have yet to be fused. The green part is then heated in the firing process during which the glue is burned out and the metal particles fuse into solid metal. The part also shrinks some during the firing step but shrinks in a controlled and completely predictable way which allows for holding very precise tolerances on the finished piece.

 

[Randy Lee]

Greetings all,

I wanted to share some of my humble observations regarding firing pins. First and foremost, my pins are made from 17-4PH stainless steel round stock. I believe a forged firing pin would be prohibitively expensive to make.

As far as factory Ti firing pins failing, there is no question that they do. The caveat to that is that any pin will fail given the right circumstances. Chipping and fracturing of the factory pins is commonly seen in guns firing either fast recoiling high velocity ammo or heavy recoiling big bore magnums. I have seen evidence of failure in both the Scandium J-framed guns as well as the .460-500 X-frames.

One of the causes of this is what is known as a contra-cou event. When the firing pin embeds in the primer and pressure builds(in the hotter loads), the primer is the first thing to move rearwards. This begins to push the firing pin rearwards before the cartridge case begins to shift back(If you fire a primed case without any bullet or powder on it you can see measurable primer shift.) Once the bullet leaves the case and begins to travel towards the forcing cone, the case then follows it's rearward path and slams against the recoil plate or breech face.

With heavy or fast recoiling loads, the firing pin can actually push back against the hammer with enough force to have it lose contact with the firing pin and slap back down. It is a nearly instantaneous event, but it does happen.
In a nutshell, the firing pin gets hammered in both directions. The factory Ti firing pins were designed to pass a drop test and not a contra-cou event. With the conical shape seen on current factory firing pins this phenomenon concentrates an excessive amount of force on it's tip. Most of the failures I have seen are chipping or fractures of the tip, although I would not be surprised if breakage occured elsewhere along the pin shaft.

For such applications I believe the firing pin tip should be a full radius dome and made of a shock resistant steel for the sake of longevity. At least for the stout magnums that will be shot with any regularity.

 

[tomcatt51]

Ever seen high frame rate slow motion film/video of the hammer when the gun is fired? I've always assumed the hammer bounced a couple times during the process.

 

[Randy Lee]

Tomcatt51,

I have seen a few, but none that have focused on this event and none with the 500 or the j-frame Sc guns where this was the focus.

I have however seen cases where the case hardened surface of a hammer was penetrated by the back face of a firing pin and resulted in a severe crater. This is why the shape of the firing pin strike face can be critical as well as the tip. It's amazing what I learned in the process of developing and testing my pin.

 

[bountyhunter]

Originally posted by Randy Lee:


With heavy or fast recoiling loads, the firing pin can actually push back against the hammer with enough force to have it lose contact with the firing pin and slap back down. It is a nearly instantaneous event, but it does happen.
In a nutshell, the firing pin gets hammered in both directions.

Thanks for the explanation. I'm not sure I understand this or why the shorter pins in a SW revo would be prone to break. The firing pins in autos are much longer and subject to the same physics. When the round fires, the primer always flows backward against the head of the firing pin. In autos with light recoil/hammer springs that unlock too quickly, the case is dragged out before the tip of the FP retracts fully and the primer shows the "wipe" track from it.

I understand the FP in the SW revo might get a rearward whack that would "bounce" the hammer from contact, and then the hammer would hit it again but the second hit would have less force than the first initial hit.

I am having rouble seeing why the primer backflow would be so lethal to the firing pin in the revo, when the much longer pins in autos hardly ever fail.

 

[Randy Lee]

There are a couple of reasons that I can think of. First, the conical tip has a much smaller impact surface area, so the stresses on the tip tend to be a bit more of an issue. In the case of the revolver (using hotter loads anyways)the headspacing can be a bit more generous allowing the primer to move back farther and a bit faster.
In a 1911 the mass of the firing pin, associated parts and therefore the inertial events are spread out over a longer time interval. Back when major power factor was 175 in IPSC and titanium firing pins were played with, chipping of the tip was a common experience. I have seen a lot of pierced primers as a result of a chipped 1911 Ti firing pin. I think both the revolver and the 1911 firing dynamics have vastly different (and directional) forces at work. Too complex for me to analyze with my wee little brain anyways.

A couple of other factors come into play as well. For guns firied DA, there are rotational forces which can apply stresses to the pin. In the case of the revolver pin(with the hammer down) the protrusion is at some nominal length sticking into the primer. At the first impact, energy has to be absorbed as the primer cup deforms. In the following contra-cou events typically the anvil of the primer is pressing in against the cup from the opposite direction. So the impact force of these secondary or perhaps even tertiary bounces may not be as insubstantial as we think.

As a sidebar, I have only seen one of the factory round tip steel firing pins chip. I honestly think material selection and tip geometry plays a critical role here.

 

[bountyhunter]

Thanks for the info. I never looked really close at the shape of the tip of the FP, so I never knew it was conical. Couldn't the stock FP tips re radiused out a bit to make them rounder on the end?