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MSD Mike
January 28, 2011, 11:51 AM
I have a NM Ruger Blackhawk in .357. The firing pin does not protrude far enough when the hammer is dropped resulting in the occasional light strike and misfire. It appears that I need to shorten the nose of the hammer a little as the firing pin protrudes properly when you push on the transfer bar. My concern is if I shorten the hammer nose what happens to the heat treating and hardness on the hammer nose? If shortening the hammer is not and acceptable cure for the problem what are my options?

Any input will be greatly appreciated.

PS. The mainspring is factory and plenty stout.

Thank you,
Mike

Sarge
January 28, 2011, 12:16 PM
First, confirm via measurement that you firing pin protrusion is too short. Industry Standard is between 0.050 and 0.055 inches. So long as you have that much FPP, an OEM strength striker spring and the cartridge is properly supported by the chamber, any primer will light off like it should. These elements work together as insurance against the worst-case scenario.

Measuring firing pin protrusion is within the abilities of any hobbyist who can read a set of micrometers. Brownells markets a little adjustable gauge specifically for this purpose. You simply take a reading from the front of the slide to the clean breechface, take another reading with the firing pin fully extended, and subtract the difference. The difference between the two figures is your firing pin protrusion.

I have done exactly the modification you suggest.

http://www.thesixgunjournal.net/repatriatedrugergp.html

Proceed at your own peril.

Scorch
January 28, 2011, 12:16 PM
If you ship it to Ruger, they will fix it.

hickstick_10
January 28, 2011, 01:09 PM
If you ship it to Ruger, they will fix it.

Best advice your gonna get right there.

MSD Mike
January 28, 2011, 01:20 PM
Thanks Sarge, at a glance I would say protrusion is as short as .025 with the hammer on the transfer bar and twice that when you push the transfer bar against the firing pin. I have the tools and will measure properly when I get home tonight. I think the only reason the gun is halfway reliable is the mainspring seems super strong.
What method did you use on the hammer nose? I was going to squeeze it between aluminum vice jaws with the exact amount exposed that I want to remove exposed and file it down being careful to keep the angle the same.
Any suggestions are appreciated.
Also, I am still a little concerned about removing the heat treating on the hammer.

Scorch, I would send the gun to Ruger but it's an older used purchase and I simply like to work on things so I think I will take a shot at it myself.
If I screw it up I will buy a Power Custom trigger and hammer and go that route.

Thanks again
Mike

Unclenick
January 28, 2011, 01:36 PM
I don't think filing down a hammer will cause you metallurgical trouble as it isn't a case hardened part. Just remember the firing pin is supposed to finish traveling forward inertially. Before you mess with it at all, check all the usual suspects:

Primers not seated firmly enough are the most common ignition issue. They should all be 0.003" or more below flush with the case head. Seating primers firmly seldom causes a problem, so better to seat too hard than too light. Also, if your cases have been reloaded a bunch of times and you do not routinely clean out the primer pockets, now may be the time. Eventually they can accumulate enough fouling to cushion the primer, thereby interfering with seating and ignition.

Cast bullets sized larger than the chamber throats and seated out far enough to find the throat before the cartridge is fully chambered can interfere with complete chambering. This is because the firing pin blow then pushes the cartridge deeper in the chamber throat by hammering the lead in and the blow is partly absorbed by that.

Both under-seated and and bullet-cushioned rounds usually fire on the second try. That's the symptom to look for. The first attempt finishes seating while the second can then fire against the now firmly positioned primer.

The firing pin tunnel needs to be clean and free of residue or lubricant gum that might impede free and rapid firing pin travel. Spray solvent clean out may help. This is something that works best with extremely thin lube or dry lube or no lube.

Have you tried a more sensitive primer? I find Federals will often fire under circumstances when others don't. This is partly due to cup thickness being on the lean side, partly to actual mix sensitivity, and partly to the cup diameters being a half thousandth or so narrower than some, which allows easier complete seating. Federal recommends that when you feel the primer anvil bottom out in the primer pocket, you seat about 0.002" deeper with this size primer (0.003" deeper for large primers). That's ideal. It slightly compresses the primer pellet between the primer cup and anvil nose, which is called setting the bridge (between the two).

Did you check that the barrel/cylinder gap is adequate size so you know the cylinder isn't too far forward. The gap should be around five or six thousandths. If it is, like, two thousandths or, worse, if you have scrape marks on the cylinder face from dragging on the back of the barrel, then you may need a shim washer that moves the whole cylinder back (a nuisance not to lose when disassembling a single action for cleaning, but sometimes needed if the factory fit was off).

Best bet is to let factory service deal with the mechanical issues. If you have any accuracy complaints, let them check that at the same time. I've had them ream chambers uniform and re-hot blue to factory color, and all free of charge, in response to such a complaint. You're out the Fedex bill, but you get a better gun in that it's had some personal attention from their more knowledgeable employees.

Sarge
January 28, 2011, 01:46 PM
Thanks Sarge, at a glance I would say protrusion is as short as .025 with the hammer on the transfer bar and twice that when you push the transfer bar against the firing pin. I have the tools and will measure properly when I get home tonight. I think the only reason the gun is halfway reliable is the mainspring seems super strong.
What method did you use on the hammer nose? I was going to squeeze it between aluminum vice jaws with the exact amount exposed that I want to remove exposed and file it down being careful to keep the angle the same.
Any suggestions are appreciated.
Also, I am still a little concerned about removing the heat treating on the hammer.

....
Thanks again
Mike

I just took a file to it Mike, taking extra care to keep the impact area flat. I'd try about 0.005 and see what that gets you. I always measure protrusion on these with the trigger held back and thumb pressure against the hammer.

Good luck & take care.

MSD Mike
January 28, 2011, 03:24 PM
All good info. Nick I will check all the other areas. I am sure the pin protrusion is short but was probably aggravated by an improperly seated primer or two. The ammo I have been shooting is off a Lee progressive and I get the odd high primer with it every now and then.

Thanks all,

Mike

James K
January 28, 2011, 06:25 PM
I don't know about the Ruger, but a good figure for firing pin protrusion is .06-07". If all else is OK and I wanted greater protrusion, I would not gain it by messing with the hammer but by replacing the firing pin.

The description is a bit puzzling. The firing pin should not protrude at all unless the hammer is pushing on the transfer bar (i.e., the trigger is being held back as in firing). If it is protruding at any other time, something is wrong.

Jim

MSD Mike
January 29, 2011, 12:08 PM
Sorry for not being more clear. It was checked with trigger pulled and pushing the hammer forward and protrusion was short. When holding the hammer back, pulling the trigger and pushing on tge transfer bar with a ball point pin protrusion is fine. My thought was to shorten the nose of the hammer a bit allowing it to move the transfer bar/ firing pin further. Of course a longer firing pin would achieve the same thing. I will have to take it out and measure to see if its within spec,

Thanks
Mike

drail
January 29, 2011, 12:18 PM
On a Ruger SA revolver the hammer has to strike in such a way that most of the force is placed on the frame. If you clearance the hammer so that all of it's force is placed on the transfer bar there is a high probability that the transfer bar will crack and break. It it a fine balance and precise fit. I would send it back to Ruger. It sounds to me like there may be a piece of crud in the firing pin recess that is preventing full travel.

Unclenick
January 29, 2011, 06:22 PM
As I mentioned, it's supposed to finish up striking inertially. If I take my own Blackhawk (.41 Mag) and press the trigger and let the hammer press the transfer bar, I get about 27 thousandths pin protrusion. If I push in on the transfer bar manually, I get about 38 thousandths protrusion. If I use a ballpoint pen to push in on the firing pin itself, I get about 50 thousandths protrusion. So it sticks out about twice as far with the ballpoint pen pushing on the pin, and this gun has never had a misfire that I can recall.

So I just think you're likely barking up the wrong tree. This is more likely crud or thickened oil in firing pin tunnel or high primers that are the issue. One other thought: Be sure you didn't accidentally put small rifle primers into your cases, as they will be harder to fire than pistol primers.

The way I measured the firing pin protrusions is with a 12" caliper's depth probe. I just ran it in through the muzzle and touched down just to the side of the firing pin hole, then stopped the back of the beam against the muzzle (gently) and pressed the zero button. I repeated with the firing pin held in the other positions and looked at the minus number of thousandths. It's not perfect, but probably within two or three thousandths. Unfortunately my depth mike's extensions only go to 6" and my barrel is 6.5", or I could give you a tighter number.

Sarge
January 29, 2011, 09:00 PM
Uncle Nick posted an excellent step-by-step procedure for taking measurements to determine how much each part in the 'transfer chain' affects firing pin protrusion. It is almost exactly the protocol I use, so I'll copy and paste here with numbering and comments.

As I mentioned, it's supposed to finish up striking inertially.

1. If I take my own Blackhawk (.41 Mag) and press the trigger and let the hammer press the transfer bar, I get about 27 thousandths pin protrusion.

2. If I push in on the transfer bar manually, I get about 38 thousandths protrusion.

3. If I use a ballpoint pen to push in on the firing pin itself, I get about 50 thousandths protrusion.


So it sticks out about twice as far with the ballpoint pen pushing on the pin, and this gun has never had a misfire that I can recall.


#2 is the reading that matters

To be meaningful, #3 must be done with a flat ended device which holds the 'hammer side' of the firing pin flush with the frame- but no deeper. This measurement tells you the maximum your firing pin is capable of traveling.

The perfect result would be for the pin to extend between 0.050 to 0.055 inches with the hammer held hard into the transfer bar while the trigger is held back- and negative protrusion, or no protrusion whatsoever, when the hammer is at rest without the trigger held back.

FWIW the numbers I posted above came from Brownells and they were quoted to me as 'Industry Standard'. This is meaningful because you can bet those figures provide primer manufacturers with some idea of how thick, and malleable, they need to make their primer cups.

A word on inertial firing pins- the classic example is the 1911-A1 pistol. When of proper length, the pin will not touch the primer with the hammer at rest. The difference between an inertial pin, like the 1911's and a direct impingement pin, like the Blackhawk's, is mass. The 1911's firing pin is many times heavier than the Blackhawk's; it simply must be because that mass is needed to carry the pin beyond its normal resting place with enough force to reliably fire a primer. The little pin in the Blackhawk simply does not have enough weight to reliably act as an inertial firing pin.

Unclenick
January 30, 2011, 10:15 AM
I should clarify: Because that step in the hammer nose stops it moving forward when the transfer bar is not yet hard against the frame, inertia will cause the bar to slap that last hundredth of an inch or so forward to push the pin flush with the frame. I suppose pin inertia by itself might add another little bit, but it certainly isn't expected to have enough inertial mass to plow through the full length of the pin strike. It has something more behind it for most of that.

My curiosity is up now. I'm thinking to take an old case and turn the front of the rim back until I can just get a freshly seated primer positioned where the transfer bar push on the pin ends, then see how much of a mark the pin inertia alone can make on it. Not expecting much penetration, but do expect to see something.

MSD Mike
January 30, 2011, 02:53 PM
A little additional info,
I had a little time to actually measure the firing pin protrusion today. When holding the trigger back and pushing the hammer forward it is .018 and when pushing on the transfer bar to move the firing pin out it is .039. My caliper isn't long enough so I used a small steel block against the recoil shield and measured its movement. I needed three hands to achieve all this so my wife helped. I have not had time to remove the firing pin to check for cleanliness but when pushing on it it moves freely. Cylinder gap with the hammer cocked and pushing the cylinder backwards is .004. This is a little tight so when I have time to work on it again I will measure head space to make sure its ok.
To eliminate ammunition I carefully loaded 50 rounds of 38 special using a hand primer and double checking for high primers.
Load is new Starline brass, Winchester primers, 4.2 grains of Bullseye and a 158 Grain LSWC for a little over 800 FPS (Out of my 4" Model 19). Two out of 50 failed to fire and all had shallow primer dents. One FTF round one worked the second try and the other did not. When trying the second round in my 19 it went off the first try.

Thanks for everyones input

Mike

Unclenick
February 1, 2011, 10:45 PM
Your transfer bar flush position is the same as mine, but your pulled trigger position is 0.010" short of mine. That could be the problem as it will effect the transfer bar impact inertia. Coupled with a narrow barrel/cylinder gap, the combination could certainly be responsible. So, quite possibly, your original solution is the right answer after all. Do check that the hammer nose isn't running into a built-up of crud that holds it back, but that seems unlikely.

I'd call Ruger for feedback on the pulled-trigger pin protrusion and the barrel/cylinder gap, or else pick up a copy of Kuhnhausen's shop manual (http://www.gunbooks.com/ruger_sa.html) on the single-action Rugers. I don't have a copy of that particular one of his shop manuals (though you've got me thinking to get one now) but it's bound to have that information in it. It's his kind of detail. If you go to working on the hammer, you might want to get some high spot blue to help you scrape or stone the nose to the hammer flush to the frame so you get good flat impact, and don't have a slightly slanted leading edge impacting and driving an indentation into the frame.

Sarge
February 1, 2011, 11:13 PM
Something I've run into with transfer bar equipped Rugers... if you look hard at the side of the bar next to the firing pin, you may see a bright spot on casting burrs; or perhaps a high or unfinished edge near it's top. These guns are mass-produced and sometimes, it really shows in places like this.

Ideally, the bar would rest precisely parallel to the corresponding frame surface it meets during the firing process. Such a relationship would insure that the firing pin gets due inertia from the bar and that none of it is wasted by interfering surfaces. With that in mind you may stone away those high contact points.

That process was one of the steps used to correct the old GP-100, referenced in a linked article earlier in this thread. It can gain you several thousandths of firing pin protrusion.

I'd still suggest that you take a measurement with the firing pin pressed flat against the frame, using a suitable implement. (Reading #3) This will give you the max protrusion possible with that pin, in that frame.

MSD Mike
February 2, 2011, 09:42 PM
One more measurement, clearance between the shell head and the recoil plate is .011. Based on that the firing pin cant hit it very hard. I believethe fix is removing a little from the nose of the hammer but I am concerned about keeping it flat. Oh well, I will give it a try and replace it if I mess it up. I would send it in but i am determined to learn all I can.
By the way, Kuhnhausens manual will be here in a couple of days


Mike

Sarge
February 2, 2011, 10:30 PM
I do meatball gun surgery when the problem and the fix are clear to me; but that Kuhnhausens manual will do you a lot more good than I can, Mike.

I've got one of Jerry's books for the 1911 and it's a gem.

MSD Mike
February 3, 2011, 09:45 AM
I agree, I have his manual for my Smith revolvers and it is a great resource,

Mike

MSD Mike
February 27, 2011, 03:03 PM
It seems to have worked. I filed down the nose of the hammer enough to increase pin protrusion by about .012. Ignition was reliable and primer dents looked more normal.

Thanks for everyones input,

Mike