Light primer strikes for 625

[chopperman]

My friends 625 has light primer strikes when double action firing. I let him use my ribbed mainspring to eliminate that, but it still does it. He's getting an extended fire pin for it, but I think it's something else. I looked at the fire pin protrusion from the frame recoil plate and it looks good without any measurement. He does use full moon clips, I wouldn't think that could be a problem. Could headspace be a problem, I don't know what specs are on these newer revolvers otherwise I'd measure.
Stan

 

[cowboy85306]

The strain screw that applies tension to the main spring could be too short to apply the needed tension. This condition is mostly seen on used guns that someone thought they were doing a trigger job on, and found out later that , yeah, it would only set off Federal primers ( if they did not go so far that this was unreliable also ). Something else that should be considered.

 

[oldbrownhat]

The strain screw that applies tension to the main spring could be too short to apply the needed tension....

Yes, I was wondering if someone might have fiddled with the strain screw to lighten the strike. Some back it out a bit or shorten it, but this usually requires the exclusive use of Federal primers, which are the most sensitive. I tried this with mine, but ended up putting in Wolff springs and leaving the strain screw fully "in."

Here are a couple of pics. I had forgotten that I'd replaced the screw with a regular set screw (8-32)

 

[steelslaver]

If you use a regular type screw you best round the tip off some. If not eventually the end of the screw will get its threads buggered up and be difficult to remove and might mess up the frames threads.

 

[lefty_jake]

It is quite likely that the light strikes are caused by insufficient mainspring tension, but there are many other mechanical factors which can also cause light strikes. As you mentioned, one of these factors is the firing pin.

If you tell us the weight of the double action pull, that provides an approximate estimate of mainspring tension. If the double action is less than 8 lb, then mainspring tension is likely to be an issue, and if the pull is greater than 11 lb, then the mainspring is probably sufficient. In between those weights, we would need to make some judgements based on the rest of your assessment, but the trigger pull is still a useful clue.

The trigger weights I have given are approximate, but they work as basic guidelines. Of course, the double action weight is also affected by the rebound spring, but the trigger pull still gives a strong hint about mainspring tension.

There is also a more direct way to measure the mainspring tension by measuring the hammer strength with a trigger gauge. This method is illustrated in post #2 of this thread.

question about testing hammer spring weight

 

[Pig Hunter]

My 625-8 PC had that issue. I put in a longer strain screw in and that fixed it. The downside is the spring arch interfered with grip screw. The trigger is a tad heavier, but always goes bang.

 

[retired2006]

One more thing to check, that revolver has the frame mounted firing pin of course, but be sure the firing pin return spring is functioning properly. I have had some springs that were broken, or collapsed, which did not let the firing pin return fully, and would misfire because of that.
BTW, I usually install a new spring with the C&S extended firing pin in my revolvers.

 

[cowboy4evr]

you can have some " burned powder residue " in the well where the firing pin sits . I had that on a 29-10 that I bought used . It was misfiring badly when I bought it , in double action and even single action . Removing the firing pin and a good cleaning helped . I figured out they had filed down the strain screw to lighten the action . Jerry Miculek has a video showing to do that . I had to replace the strain screw as well . Regards, Paul

 

[oldbrownhat]

If you use a regular type screw you best round the tip off some. If not eventually the end of the screw will get its threads buggered up and be difficult to remove and might mess up the frames threads.

Good point. I'm pretty sure I did that with the set screw on mine, although set screws have rounded ends anyway. Still have no idea why I didn't use the original.

 

[Protocall_Design]

The setscrew (8-32 x 1/2) with blue Loctite allows for fine tuning with the gun assembled. I drill a matching hole in the front of my grips to use a hex key without taking anything apart. That way it's quick and easy to adjust on the range while shooting.You can back it off to get misfires, then tighten in 1/8 turn increments to get 100% reliability, then another 1/8 turn. For times where the spring and grip screw collide, you can put a gradual bend in the middle of the spring to clear the screw.

This type of tuning is ONLY for target and competition guns and NOT for carry or duty guns. Leave them full strength as original. If you need these, you will have no problem with the trigger pull during a pucker factor event.

 

[oldbrownhat]

The setscrew (8-32 x 1/2) with blue Loctite allows for fine tuning with the gun assembled. I drill a matching hole in the front of my grips to use a hex key without taking anything apart. That way it's quick and easy to adjust on the range while shooting.You can back it off to get misfires, then tighten in 1/8 turn increments to get 100% reliability, then another 1/8 turn. For times where the spring and grip screw collide, you can put a gradual bend in the middle of the spring to clear the screw.

This type of tuning is ONLY for target and competition guns and NOT for carry or duty guns. Leave them full strength as original. If you need these, you will have no problem with the trigger pull during a pucker factor event.

Yes, 8-32. I should have seen that when I took the pic of the original. (I've corrected it now). And I think adding the second screw was something I considered at the time, but the trigger on mine is just fine as it is so have just left well enough alone

 

[jimmyj]

Is your friend using factory ammo or reloads ?
If reloads, possible the primers are not fully seated due to primer pockets not being clean.

 

[Andy Lowry]

I used the old spent primer cap trick on a misbehaving 325. New mainspring and extended firing pin didn't fix it, but the little extra on the strain screw did. Someday I'll have to actually buy a longer screw, but it's okay for now.

 

[WR Moore]

S&W does a really good job on the length of the strain screws. That said, here and there some variation in length does happen. Strain screws are cheap.

 

[mscampbell2734]

Got to ask is your friend using a good tool to load and demoon his clips? The possibility of a bent clip can not be ignored. New clips are cheap and would eliminate that as a cause.

 

[bd629DX]

Is this a common question? I just saw this same question in another thread.
I had this problem many years ago and a local gunsmith that built PPC guns explained it to me. The S&W design doesn't pull the hammer back as for in DA as it does in SA- cycle the gun slowly in DA and you can see this. Plus CCI primers are harder than other brands. Combine these 2 things and you can have misfires in DA.

 

[WR Moore]

bd629DX-that answer to the problem assumes that the mainspring (hammer spring) has been modified or the strain screw adjusted/modified to the point where the single action hammer fall is just barely enough to ignite a primer.

Operator error can figure in here also. If one is trying to finesse the trigger release in double action and fail to pin the trigger all the way back on release, the trigger finger can relax on hammer release, allowing the trigger and rebound slide to move forward to where the rebound slide interferes with the hammer and causes a misfire.