Cylinder and Slide extended firing pin broke

[Carmoney]

Aren't we lightening our hammers to get back the velocity we lose when we lighten the hammer spring?

Exactly.

[Randy Lee]

Hi Tom,

In the ideal case you are quite right. The firing pin and hammer will travel forward together, strike the primer and thus detonate it. The hammer often will not bottom out against the frame during the firing of the gun.

However, if you look at a 625 with say .010 gap measured from the back of a cartridge case to the face of the f/p bushing, a .483 f/p, and a primer set to .008 or greater depth, the hammer's forward travel will often be stopped by the frame, and the firing pin will continue to travel forwards. This is where the ignition can get iffy. The pin's energy can be absorbed at several points along the way: the return spring, cartridge position, primer pocket depth relative to the primer seating depth, etc.

I believe the momentum required for ignition is a conserved amount. As you know momentum is a function of mass and velocity. We can either increase mass and decrease velocity, or we can increase velocity by removing mass to get to our momentum point (sorry if I'm using improper syntax)- so we're really not losing momentum- simply trading elements for our shooting pleasure .

The firing pin impressions on a fired case are misleading evidence because as the cartridge detonates, the primer is the first component to move rearwards as the bullet begins to pull out from the case. Federal primers are softer, so they tend to move more readly and envelope the f/p tip giving a false reading of how far the pin actually penetrated into the cup at the point of ignition. You can prove this to yourself by firing a primed case and seeing how much the primer pushes out of the pocket.

An interesting event(at least to me) is that upon firing, the primer pushes the firing pin back, and the hammer pushes back as well. With a very fast impulse of major rounds (185gr bullets in .45 gap brass), the hammer will actually shift back far enough to separate from the back of the firing pin. Miniscule, but detectable...

[Tom E]

Definitely makes a good case for replacing .485 firing pins with the newer .495 pins. Longer does seem questionable, breakage aside.

"With a very fast impulse of major rounds (185gr bullets in .45 gap brass), the hammer will actually shift back far enough to separate from the back of the firing pin. Miniscule, but detectable..."

Right on but I strongly suspect this is an understatement. I would expect actual bouncing when the hammer hits the firing pin and/or frame.

"the hammer's forward travel will often be stopped by the frame, and the firing pin will continue to travel forwards."

This I think is very questionable. When the hammer hits the frame, the hammer and firing pin cease to move "as one". Without the added mass of the hammer, the firing pin alone will now have less than 5% ( at most I think) of the momentum and energy it (with the hammer) had the instant before the hammer stopped against the frame. Shouldn't be enough for it to continue on it's own.

Gets a bit convoluted but interesting. Definitely makes a fella think.

I think it's time for a beer. Tom

Edited August 10, 2007 by Tom E

[LPatterson]

What ever causes extended firing pins to break caused mine to break. I finished a stage fine went to the next stage, LMR, beep, click click, click, click. Firing pin had sheared at the edge of the shape change from diameter into the pin itself. Had not packed the original pin with the rest of the parts so through the help of Alan Kies who gave me a new pin still in the package & wouldn't take anything for it except my word to do something for another shooter some day.

Edited to correct the spelling of Alan's name.

Edited August 13, 2007 by LPatterson

[10mmdave]

In the ideal case you are quite right. The firing pin and hammer will travel forward together, strike the primer and thus detonate it. The hammer often will not bottom out against the frame during the firing of the gun.

So Randy....are you saying that hammers don't contact the frame when the revo is fired or that in the ideal case it

wouldn't ??

And...to add to the "discussion"

I've been running the same extended firing pins in my steel revo's for I don't remember how long, never have had one

break but probably will have one go at this weekends Walls of Steel match in RI

Posted a couple (few !?) years ago of my problem with a 610 Classic, gun worked fine with 10mm brass but misfired

with 40 S&W brass, changed to a C&S extended and all's been well ever since.

For some they work well, for other's, not much it sounds like.

Okay, back to work.

[Carmoney]

For some they work well....

Right up until they break.

[Round_Gun_Shooter]

For some they work well, for other's, not much it sounds like.

Okay, back to work.

I am beginning to think it is a regional thing. They just seem to work in the North East. I have them in four revolvers and have never experienced a problem. I don't doubt others do, but it has never happened to me. Do I carry spare pins?? Sure but I also have a spare for my model 66-1 with the hammer mounted pin.

Regards,

[Tom E]

Do I carry spare pins?? Sure

Maybe Bob could make bandoleers for them to go with his great moonclip holders.

[Randy Lee]

In the ideal case you are quite right. The firing pin and hammer will travel forward together, strike the primer and thus detonate it. The hammer often will not bottom out against the frame during the firing of the gun.

So Randy....are you saying that hammers don't contact the frame when the revo is fired or that in the ideal case it

wouldn't ??

And...to add to the "discussion"

I've been running the same extended firing pins in my steel revo's for I don't remember how long, never have had one

break but probably will have one go at this weekends Walls of Steel match in RI

Posted a couple (few !?) years ago of my problem with a 610 Classic, gun worked fine with 10mm brass but misfired

with 40 S&W brass, changed to a C&S extended and all's been well ever since.

For some they work well, for other's, not much it sounds like.

Okay, back to work.

As the current Smith revolver is designed, the hammer will not or rather should not contact the frame where the firing pin is located. The older and more recent firing pin lengths of .495" or greater should contact the face of the primer well before the hammer bottoms out against the frame. This is especially true of the competition tuned revo. With Ti firing pins, this has to be the case in order to compensate for endshake and headspacing tolerances.

Last year, several duty guns came through my shop with the complaint of misfires. They were all new guns -factory stock. Their firing pins all measured .483 or less and replacing them with .495's eliminated the ignition issues.

If you look at my n-frame hammer, or the factory's, it has a protruding ledge below the striking face. This ledge contacts the frame when dry firing to prevent battering of the firing pin hole in the frame. I have seen two instances of modified hammers beating the frame face so much that the firing pins would stick.

There is no doubt that the C&S firing pins can solve an ignition problem, but as Mr. Carmoney points out- they do have a higher percentage of failures in competition guns than factory versions.

I believe there is also a thread involving breaking a firing pin spring in which a C&S pin was used...

[10mmdave]

As the current Smith revolver is designed, the hammer will not or rather should not contact the frame where the firing pin is located. The older and more recent firing pin lengths of .495" or greater should contact the face of the primer well before the hammer bottoms out against the frame.

Okay, I understand what you was saying now.

[Tom E]

With the hammer fully forward the FMFP should have the same protrusion beyond the recoil shield you would see with a hammer mounted pin. It is not an inertial pin, it acts like a hammer mounted pin except (obviously) isn't attached to the hammer. Tom

[imashooter2]

For the record, I sent the broken stub back to C&S and they replaced it quickly with not a word of protest. Not sure exactly what I'm going to do with it though...

They seem to like them over on the S&W Forum. Maybe I'll try to trade it for one of the .495 factory pins.