[DrMLap]

I own a S&W model 19-3 revolver that I reload for. I go as often as I can to the range to test out my recipes. For the last couple of months, I have been getting the occasional misfire due to light strikes on the primer. I am using CCI 500 brand primers. I know they are light strikes because each time, after waiting a half minute, I open the cylinder, rotate 1 position clockwise, close the cylinder, and fire again. Each time the round goes off as expected. This happens maybe once every 100 to 200 rounds.

I would provide pictures but I keep forgetting to save the round that misfired. I remember each showing a less than definite depression in the primer. On the second try, after a successful firing, firing pin depression is much more definite.

Obviously, I will be taking my gun to my gunsmith. What do you think my gunsmith will tell me? Should I be getting a new firing pin? Is it a contamination issue? Is it a wear issue?

 

[JBelk]

The first thing to check is the hammer spring strain screw in the front strap of the grip, down low. Be sure that's screwed all the way IN.
THe rest is internally, but I'd question primer seating first. Light strikes are often primers not seated the bottom of the pocket.

 

[DrMLap]

The first thing to check is the hammer spring strain screw in the front strap of the grip, down low. Be sure that's screwed all the way IN.

Yes, as others have suggested, I will be checking my strain screw. As to screwing it all the way in, I'm not comfortable with that. A couple of years ago I got a trigger job done by my gunsmith. He did an excellent job. My trigger might be a hair less than 2 lbs. And smooth. If I screw the strain screw all the way in, I could ruin that. But I will give it maybe a quarter turn (if it is not already bottomed out) and see if that improves the issue. If that doesn't work, then I will definitely change primers.

 

[JBelk]

Your hammer hasn't got enough energy because the spring is partially relaxed. Also note, when the strain screw is not tight it straightens the hammer spring making it longer towards the pivot. That causes an interference at the very end of the cocking cycle that pushes on the end of the hammer spring which loads it in the wrong direction resulting in breakage.

The 'trigger job' is 100% the problem and something has to be reversed to get it back right. I predict your trigger pull wont be affected but you will notice a different feel at the end of the hammer throw in single action. The original deluxe S&W was the 'Registered Magnums'. Their triggers are light enough to enable a 'push off' where the hammer can be dislodged from the sear by pushing on it with a thumb, BUT the gun will not fire that way unless the trigger is also fully pulled at the same time, by design.

 

[Mainspring]

If I screw the strain screw all the way in, I could ruin that.

Right now you own an expensive door stop. Don't mess around trying other fixes until you turn the screw in all the way, it's the quickest, cheapest, most instantaneously reversal 'fix' you could attempt.

Please note that the proper way to adjust a Strain Screw is to shorten it, rather than unscrewing it. If it is already tight then replace it with a new one.