Light strikes with M642.

[Bruce H.]

I have a model 642 which I have had for four years now. All of the springs are factory. I have not messed with the internal lock mechanism. In the past, I would occassionally have a light strike where the round would not fire the first time. Maybe one round out of 50. But today I took it to the range and approx. 1/3 of my rounds didn't fire the first time. In each case, when I tried to fire them a second time they fired normally. When the rounds would not fire, I opened the cylinder and it was very obvious which ones didn't fire. The firing pin impression in the primer of those which didn't fire was very small compared to the impression in the primers of the rounds that fired. I have recently put a nice wood aftermarket grip on the gun, but I checked and there is no way that the screw is interfering with the mainspring or hammer strut. The ammo I used was 38 special reloads that I reloaded myself. I have been shooting this same batch of reloads in my Blackhawk with no problem whatsoever. I use a Dillon Press and I know that my reloads are not a problem. They work fine in my other revolvers. What could cause this occasional problem that seems to be getting worse? I have read that some people replace the firing pin with a longer firing pin when they have this problem. How difficult is it to change the firing pin in a model 642?

 

[Bruce H.]

I have a model 642 which I have had for four years now. All of the springs are factory. I have not messed with the internal lock mechanism. In the past, I would occassionally have a light strike where the round would not fire the first time. Maybe one round out of 50. But today I took it to the range and approx. 1/3 of my rounds didn't fire the first time. In each case, when I tried to fire them a second time they fired normally. When the rounds would not fire, I opened the cylinder and it was very obvious which ones didn't fire. The firing pin impression in the primer of those which didn't fire was very small compared to the impression in the primers of the rounds that fired. I have recently put a nice wood aftermarket grip on the gun, but I checked and there is no way that the screw is interfering with the mainspring or hammer strut. The ammo I used was 38 special reloads that I reloaded myself. I have been shooting this same batch of reloads in my Blackhawk with no problem whatsoever. I use a Dillon Press and I know that my reloads are not a problem. They work fine in my other revolvers. What could cause this occasional problem that seems to be getting worse? I have read that some people replace the firing pin with a longer firing pin when they have this problem. How difficult is it to change the firing pin in a model 642?

 

[Bullseye Smith]

First it could be your reload's, the primer not being at full seat will do it. How old is the 342, did you buy it new? take the stocks off and look at the main spring, if both ends look alike and check to see what color it is. Right now that is the best I can do for you. Later John

 

[HEADKNOCKER]

Make sure the cylinders bores are clean/spotless, carboned up bores could cause the rounds not to seat till there struck by the firing pin
I'd probobly put a NEW mainspring in it & maybe a extended C&S firing pin in it if it's a 642-2
Check for excess endshake or possibly the endshake screws spring loaded tip..
As Bullseye Smith Said Check your reloads, try it with factory Ammo, & if it was bought used it could have a reduced power Wolff Mainspring
Good Luck & Welcome to The Forum Bruce H
Gary/Hk

 

[TNDave]

Originally posted by Bullseye Smith:
the primer not being at full seat will do it.

This is usually it.

 

[stevieboy]

Check the strain screw on your grip frame. That's what maintains tension on your main spring. Yesterday I had the exact same problem with my 686SSR. I pulled the grips, tightened the screw, and was good to go. Later, I "fixed" the problem with a little GunTite on the screw.

 

[machinisttx]

Originally posted by stevieboy:
Check the strain screw on your grip frame. That's what maintains tension on your main spring. Yesterday I had the exact same problem with my 686SSR. I pulled the grips, tightened the screw, and was good to go. Later, I "fixed" the problem with a little GunTite on the screw.

J frames use coil springs, not the leaf spring of the K, L, or N frame. There is no strain screw on a J frame.


I suggest putting in a new mainspring, along with making sure the hammer isn't dragging.

 

[Bruce H.]

I installed a heavier Wolff mainspring last night, that I had sitting around. I will try shooting the same ammo next week to see if there is an improvement. Also, I am going to order a longer firing pin from Cylinder and Slide and will install that when it arrives. Thanks for the input.

 

[Gearhead Jim]

The Blackhawk really whacks the primers, giving lots of excess power to pop each one. The J-frames are closer to the edge of reliability, to get a lighter DA pull. Primers that are not fully seated are the most common cause of misfires, the face of the primer normally needs to be slightly below the surrounding case head.
Or, crud under the ejector star can cushion the firing pin hit a little. Bad crud will prevent the cylinder from closing, but a little...

 

[bountyhunter]

Originally posted by machinisttx:

Originally posted by stevieboy:
Check the strain screw on your grip frame. That's what maintains tension on your main spring. Yesterday I had the exact same problem with my 686SSR. I pulled the grips, tightened the screw, and was good to go. Later, I "fixed" the problem with a little GunTite on the screw.

J frames use coil springs, not the leaf spring of the K, L, or N frame.

Yes, and coil springs are notorious for "stacking" as they age where the coils move laterally and reduce spring force. Try some new ammo and rule out the reload problem, then replace the mainspring.

 

[bountyhunter]

Originally posted by Bruce H.:
I installed a heavier Wolff mainspring last night, that I had sitting around. I will try shooting the same ammo next week to see if there is an improvement. Also, I am going to order a longer firing pin from Cylinder and Slide and will install that when it arrives. Thanks for the input.

Save your money, a longer firng pin does ABSOLUTELY NOTHING to increase striking force. I tested the C+S pins, they don't improve strike energy at all.

 

[DixieHacker]

You may want to check the firing pin to make sure part of it did not break off. My 642 had the very tip of the firing pin break off, while the rest remained in tact.

This resulted in light strikes and misfires. A trip back to S&W resulted in a quick fix.