Fitting hammer nose

[Owly]

I'm fitting a new Power Custom hammer nose onto my 66 no dash. Install was straight forward. I'm fairly confident I got the rivet expanded properly. My question is, does anybody know the proper firing pin protrusion measurement for a K-frame Combat Magnum?

The instructions included with the Power Custom hammer nose kit called for .045"-.062" measured from recoil shield to tip of hammer nose. Mine was measuring quite long at .067" so I managed to file it down to .060" protrusion.

I fired a dozen 38 specials and primer indentations are VERY prominent.
Likely too prominent as I can see a dimple (actually a small protrusion) in the center of each primer strike which I assume was made by the primer cup contacting the primer anvil during firing.

Should I shorten the firing pin another .005"?
Suggestions?

 

[armorer951]

The only protrusion gage I have is among the tools provided for the S&W L-frame refit, and requires protrusion of the hammer nose to be no more than .060". I'm not sure this recommendation applies to K-frames, but I suspect that it does. I couldn't find a notation of this particular factory specification in any of my armorer notes. All of the K-frames I have measure below .050".

Perhaps a call to S&W Customer Service could confirm this spec?

 

[Owly]

Thanks for the info. I'm pretty sure .060" is too long judging from my spent primers. I'll pull the hammer back out and file it down another .005-.010" and see how it shoots.

 

[Bushytale]

Some of my K frames measure .055 and .054 from the factory. Others measure as low as .046. The info I have seen says .062 is max. I fitted a Power FP recently on a 66-1 and it started out at .067 also. I ended up at .059.

I would leave it at .060 unless you get pierced primers.

 

[scooter123]

You probably have a protrusion gage in your pocket, it's called a Dime. Way back when there was a test for fiting pin protrusion called the Dime test because you could easliy see if the protrusion was even withthe rim of a dime held on the recoil shield.

I had to replace a short firing pin installed at the factory on my 19-3 way back in 1972, which was why it looked unfired when I purchased it used a few years back. I used the same Power Custom kit you are using and used an Eze-Lap diamond file to fit the protrusion and round the tip so that the protrusion matched the Dime Test plus just a whisker. Now instead of a 70% failure rate with CCI Magnum primers in single action it is 100% reliable in either single or double action. BTW, with the short nose that came from the factory it would not fire one single hand load that featured a CCI Magnum primer in double action and had a 33% failure rate with CCI standard primers. Frankly I'm not sure how it got through the firing test at S&W when it was new in 1972.

Tip, get yourself an Eze-Lap Diamond file in the Fine grit, it will make tuning the tip and rounding it with the correct dome shape quite simple. The are in the catalog and MSC Industrial Supply on the Net.

Fine, 2" Length of Cut, Single End Diamond 05125232 - MSC

 

[chief38]

While the spec's may call for .045" - .060" the more important factor are the Primer hits themselves on that particular Revolver. You can learn a lot from the spent primers out of a particular Revolver. I'd personally make it what is needs to be (within the guideline spec's) so the primer hit is a good solid one but not over penetrating. That just means adjusting it until the Primer hits are good, BUT before shortening the Hammer Nose, please check your End Shake measurement - just in case that needs adjustment as well because that affect how far the Hammer Nose goes into the Primer if it needs to be fixed to bring into spec.

 

[Owly]

Some of my K frames measure .055 and .054 from the factory. Others measure as low as .046. The info I have seen says .062 is max. I fitted a Power FP recently on a 66-1 and it started out at .067 also. I ended up at .059.

I would leave it at .060 unless you get pierced primers.

I fired some more rounds tonight and I think I'm going to leave the hammer nose alone for now. Fired a dozen 357 mags with CCI550 mag primers. All primer hits looked normal. Fired several dozen 38s with CCI500 standard primers. Exerienced the odd anvil indentaion on about 30% of these primers, but all rounds went off with 100% reliability in SA and in DA and no primers were punctured or ruptured.