firing pin protrusion s&w

DB · 11-05-2006, 02:20 PM

I just bought a new S&W model 649 .357 J-frame. Upon close examination, with the hammer down, the frame mounted firing pin is obviously shorter and more pointed in shape than my 3 year old 637 or any other S&W frame mounted firing pin model I own. Primer strikes are somewhat smaller than with my other S&W revolvers too. However, I wouldn't go as far as to exactly call them "light strikes". I have run about 150 rounds through the revolver with no malfunctions. I wrote Smith & Wesson asking about the proper measurement for the firing pin protrusion from the bushing and if indeed they have redesigned the pin. The only answer I got from them is that pins measure different lengths, and as long as I'm not experiencing light strikes, then don't worry about it. They did offer to let me send it in for them to inspect at the factory at no charge if I wish. I guess that I shouldn't be worried if I'm not getting misfires. I would feel better if I knew that the revolver's firing pin was within specifications though.

GrantCunningham · 11-06-2006, 08:15 AM

Every manufacturer seems to have a different idea as to what constitutes sufficient firing pin protrusion. Of course, some of this has to do with the force of hammer impact (spring pressure.)

It's not unusual to find some guns (notably Rugers) with protrusion around .042". I'd consider that to be about the bare minimum, though the factory may disagree vehemently. :lol:

When I set protrusion, particularly on a gun that's had action work, it's in the .050" to .053" range for best iginition reliability.

As to whether yours is too short, I'd say that if the gun is completely reliable with all primers (test particularly with CCI Magnums, which are the hardest on the domestic market) then you're good.

DB · 11-06-2006, 06:17 PM

Thanks Grant... Actually the protrusion with the hammer down measures only .032". With a punch forcing the firing pin all the way to its limit in the channel the protrusion measurement is about .042". It appears that S&W has redesigned the firing pin. Not only is it shorter, but instead of having the traditional fully rounded, sort of blunt tip that strikes the primer, it has a tip which posesses a definite cone shape and is sharper at the end. This is a different shape than their frame mounted firing pins of even a short time ago. I think I'll take your advice and try a box of CCI to make sure it'll reliably ignite CCI's relatively hard primers. Thanks again.

GrantCunningham · 11-06-2006, 06:46 PM

.032"?? Wow, that's shallow. Assuming that the headspacing was as tight as possible (as in "the case heads pass the recoil shield with less than .001" clearance"), allowing for .006" of primer seating depth would only give .025" FP travel! I can't imagine that working for very long...

I'd bet that you've got a defective FP. I've just recently finished working on several brand new "J" frames - a Model 60, 642, and 640 - and none of them had a FP matching your description.

DB · 11-07-2006, 03:46 AM

Actually case head to recoil shield is measuring about .007". So, headspace is less than tight as possible, but still within my understanding of the specifications. I did a little searching on the web and found a thread on another site (brian enos forum) which a guy talks about S&W changing their firing pins to a shorter and more conical shape, as well as now making them out of titanium. Someone brought up that they'd heard this was done in order to pass California drop tests. Oh well... Since they are cheap, and I like to tinker, I think I'll order another firing pin and see what I get. I really don't want to send the gun back to S&W unless I can actually document misfires. Thanks again.

11-05-2006, 02:20 PM	#1
DB Junior Member Join Date: Apr 2004 Location: Georgia, USA Posts: 11	Has S&W Changed Their Firing Pins (Again)? I just bought a new S&W model 649 .357 J-frame. Upon close examination, with the hammer down, the frame mounted firing pin is obviously shorter and more pointed in shape than my 3 year old 637 or any other S&W frame mounted firing pin model I own. Primer strikes are somewhat smaller than with my other S&W revolvers too. However, I wouldn't go as far as to exactly call them "light strikes". I have run about 150 rounds through the revolver with no malfunctions. I wrote Smith & Wesson asking about the proper measurement for the firing pin protrusion from the bushing and if indeed they have redesigned the pin. The only answer I got from them is that pins measure different lengths, and as long as I'm not experiencing light strikes, then don't worry about it. They did offer to let me send it in for them to inspect at the factory at no charge if I wish. I guess that I shouldn't be worried if I'm not getting misfires. I would feel better if I knew that the revolver's firing pin was within specifications though.

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11-06-2006, 08:15 AM	#2
GrantCunningham Junior Member Join Date: Dec 2005 Posts: 17	Every manufacturer seems to have a different idea as to what constitutes sufficient firing pin protrusion. Of course, some of this has to do with the force of hammer impact (spring pressure.) It's not unusual to find some guns (notably Rugers) with protrusion around .042". I'd consider that to be about the bare minimum, though the factory may disagree vehemently. :lol: When I set protrusion, particularly on a gun that's had action work, it's in the .050" to .053" range for best iginition reliability. As to whether yours is too short, I'd say that if the gun is completely reliable with all primers (test particularly with CCI Magnums, which are the hardest on the domestic market) then you're good.

11-06-2006, 06:17 PM	#3
DB Junior Member Join Date: Apr 2004 Location: Georgia, USA Posts: 11	Thanks Grant... Actually the protrusion with the hammer down measures only .032". With a punch forcing the firing pin all the way to its limit in the channel the protrusion measurement is about .042". It appears that S&W has redesigned the firing pin. Not only is it shorter, but instead of having the traditional fully rounded, sort of blunt tip that strikes the primer, it has a tip which posesses a definite cone shape and is sharper at the end. This is a different shape than their frame mounted firing pins of even a short time ago. I think I'll take your advice and try a box of CCI to make sure it'll reliably ignite CCI's relatively hard primers. Thanks again.

11-06-2006, 06:46 PM	#4
GrantCunningham Junior Member Join Date: Dec 2005 Posts: 17	.032"?? Wow, that's shallow. Assuming that the headspacing was as tight as possible (as in "the case heads pass the recoil shield with less than .001" clearance"), allowing for .006" of primer seating depth would only give .025" FP travel! I can't imagine that working for very long... I'd bet that you've got a defective FP. I've just recently finished working on several brand new "J" frames - a Model 60, 642, and 640 - and none of them had a FP matching your description.

11-07-2006, 03:46 AM	#5
DB Junior Member Join Date: Apr 2004 Location: Georgia, USA Posts: 11	Actually case head to recoil shield is measuring about .007". So, headspace is less than tight as possible, but still within my understanding of the specifications. I did a little searching on the web and found a thread on another site (brian enos forum) which a guy talks about S&W changing their firing pins to a shorter and more conical shape, as well as now making them out of titanium. Someone brought up that they'd heard this was done in order to pass California drop tests. Oh well... Since they are cheap, and I like to tinker, I think I'll order another firing pin and see what I get. I really don't want to send the gun back to S&W unless I can actually document misfires. Thanks again.