M&P 340 Firing Pin Sparks?

[TheTinMan]

I was dry firing my new M&P 340 with plastic snap caps and noticed something very odd. Sometimes there is a small spark between the blast shield and the back of the cylinder. It appears to be coming out of the firing pin tunnel.

I have disassembled the gun except for the cylinder and the firing pin mechanism. I am not familiar with how to disassemble the transfer bar (right term?) and firing pin. I have Kuhnhausen's book but did not find the information there (could've missed it though).

I did lubricate the firing pin with CLP.

Is this "normal"? If not, what should I do to fix it?

 

[TheTinMan]

Note - I just found instructions for removing the new style firing pin in the FAQs here. Made time to disassemble the gun.

After removing the firing pin spring, I put the firing pin back in the tunnel and moved it back and forth. There is a point in its travel where it catches just a little bit. I cleaned out and inspected the tunnel as best I could but the catch is still there. Looking closely at the firing pin itself, there is a slight bulge-like irregularity close to the end which strikes a primer.

Should I (a) try to round out the shaft of the firing pin , (b) get a replacement firing pin, or (c) try something else?

 

[rustypigeon]

My 642 has an occasional spark also. I would not worry about it. That pin moves pretty fast. If it rubs against the channel it could produce a spark. Even if you replace the parts, the new parts will also likely have some contact with eachother.

 

[TheTinMan]

S&W tech says sparks are perfectly normal. Titanium firing pin going through steel firing pin bushing. She said that fit needs to be really tight there to avoid primer flow when shooting .357 Magnum rounds.

I still think it's a bit weird.

 

[hsguy]

Use the Google forum search function for "firing pin sparks" and you will find many threads about the subject. Seems to be a frequent, if not normal occurrence.