My S&W 625 is not firing reliably on double action. My gunsmith replaced the firing pin with a new one. Before it wasn't firing at all in double action. Now it fires part of the time in double action. It goes off every time in single action. The spring tension screw is all the way down to give maximum tension on the hammer.

Sounds like it`s time for a new mainspring. I shoot, (or used to) shoot double action exclusively and when this problem surfaced, replacing the mainspring solved my trouble. It` a simple DYS swap.
Welcome to the forum.
Jim

Welcome to the Forum.

Did you buy this revolver used? I agree, replace the mainspring.

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John 3:16
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If you bought the gun used a previous owner may have shortened the strain screw. Try a spent primer with the anvil removed under the strain screw.

thats a good idea

Yes, welcome aboard....

Questions:

This is a .45 ACP....?

Are you using moon clips? Have you miked them to see how thick they are?

Have you checked the headspace with the gun loaded?

Have you checked endshake?

When the gun misfires, have you checked the primer to see what it looks like and how deep the light strike is?

Have you tied any .45 Auto Rim ammo or reloads if you reload?

Is this happening with factory ammo, handloads or both?

Unless the mainspring is out of spec it is going to be a headspace problem. Put rounds into the gun, close the cylinder and measure the headspace gap between the recoil shield (breechface) and the casehead and make sure it is within spec. A 625 should run .45 ACP ammo with no clips if the headspace is correct. If it will not then it needs a trip back to The Mothership for correction if your local smith doesn't have the expertise to correct it...

Bob

Not all of the 625s were chambered to allow “loose” loading without clips. Try using moon clips or Auto Rim brass.

Kevin

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Do you know which ones were not so chambered?

I've had both 25 and 625 and everyone will headspace without clips. The only 45 ACP revolver that I knew of that will not were some of the original Colt new service.

As above BUT..."Put rounds into the gun, close the cylinder and measure the headspace gap between the recoil shield (breechface) and the casehead and make sure it is within spec" DO NOT USE LIVE AMMO, SNAP CAP OR NEW BRASS WITHOUT PRIMER. As a RN I get tired treating unloaded gun shot Pts in the Emergency Room.

Could be a few issues.

* loosened mainspring strain screw (or cut too short) or bad or lightened spring.
* timing could be off and FP might not be aligned properly.
* cylinder stop could not be holding cylinder properly in place
* cylinder has too much front to back slop.

Newer .45ACP revolvers, which I believe includes all Model 625 revolvers, have some sort of a ledge inside the chamber, but I am quite sure that they are NOT designed to properly headspace the case. I have a cut-down 25-2, a 22-4 and a 325PD. Loading the 25-2 sounds and feels like six clicks; loading the others is a more or less muffled squish into place. For years the newer guns seemed to work OK, although I never really trusted them without clips. Finally, within the last year or so, I got some failures to fire with the 325.

The new guns are obviously designed solely for clips. If they actually work without them, fine, but don't count on it. S&W didn't.

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Formerly Model520Fan

I've had:
25-2 (3)
625 Mountain Gun (3)
625 1989 (1)
625-7 PC (2)
1917 (2)
..and zero issues running without clips.

Every gun is an individual. We don't know what the condition of the OP's gun is, or the history of it's use or modifications. Just because other guns worked without moon clips doesn't mean this one will, even if they were next to each other on the assembly line.

If the OP isn't using moon clips, that is where I would start. It seems silly to me to shoot an auto caliber revolver without them, because then you have to poke out the empties one at a time like a single action Cowboy gun.

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Are you using factory loads or reloads? I had Issues with my 625-8 PC like that. A longer strain screw fixed the issue. The primer on the old strain screw will let you know if that is the problem. The only .45 ACP revolver that was bored through that requires clips was the first Colt 1917's at the very beginning of our involvement in WWI. If using reloads with too much crimp will require clips. Factory spec. ammo should require no clips.

All S&W .45 ACP revolvers should fire without using moon clips. However, there were some that were built in the '80s and '90s where S&W was a bit sloppy with the chambering and clips were needed. This was written up in gun rags of the day.

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John 3:16
WAR EAGLE!

Brian Pearce wrote an article about it. I do not have a copy but maybe another member can summerize it for you.

Kevin

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Unshared knowledge is wasted.

I sold a 625 to a customer back in '08 or '09 and told him he didn't need to use clips and another old timer concurred. Ours worked like champs. Come to find out his New one wouldn't fire reliably w\o the clips and the owner's manual specifically said you need to use clips. So I'm pretty sure some 625s may need to use clips.

First replace the mainspring and mainspring tension screw

I have a 625 PC that has to use moon clips. I reload auto rim so it is not a problem for me. The strain screw was loose when new on two new ones that I removed from the box.

I used 50 rounds of reloads [.45 ACP not .45 Auto Rim] with Wilson Combat full moon clips. Much better performance. I had a few round not go off on double action but all went off on the second try. I've got a new hammer spring coming from Wolff. I've not yet tried the primer cup shim technique but will give it a try.

Just curious as to what primers you are using, definitely try the primer over the strain screw especially if the new mail spring doesn’t work any better, Larry

Guess bottom line for me would be if I bought a S&W .45 ACP revolver brand new and it had a headspace shelf that was "supposed" to be there for headspaceing the rounds and didn't, that is a factory defect which they would be replacing.

If S&W could make them right in 1917 they should be able to do so now...

Bob

Korum...just wondering...what exact model of 625 do you have? New one, JM, PC, older 1989... Just wondering when this gun was made...

Thanks...Bob

When S&W first offered the 625 it was a period when Steve Melvin and the British were taking over and pushing CNC machines into production. There were quite a few problems with these guns in the beginning and the questions of moon clips or not was a hot topic. Not to mention finding uniform and correct moon clip thickness.
Auto rims took care of this

So first off I would be very surprised to find a bad SS main spring
Measure the mainspring weight recommend 45-52 oz. Adjust
Remember SA hits harder moves farther than DA
Measure headspace. Wedge cylinder back .093” to .098”

Finally if this is an early 625 with Pachmayr grips it’s possible the grip screw is hitting the mainspring. This wasn’t discovered until long after the first run was released by gunsmith Ron Power. It was hushed up by the factory but they very quickly changed grips. The screw was making contact with the mainspring as it arched into full hammer profile.

Rick

When a revolver misfires in double action, my first thought is "What is the double action pull weight?" What I really want to know is "how much tension is there on the mainspring?" And as garbler said, the best way to judge the mainspring tension is to measure the weight needed to move the hammer. But even though the rebound spring, and internal friction, can affect the double action pull weight, that weight still gives a good approximation of mainspring tension. So if the pull is less than 8 pounds, then a longer strain screw or a shim is probably the answer. And if the pull is over 11 pounds, then there is some other problem, and I know I would not want to make the pull heavier. If the pull is between 8 and 11 pounds, then knowing exactly where it is still gives hints about how to proceed.

And for anyone working on these problems who has no way to measure pull weight, I would say "stop." Either get a trigger pull gauge, or makeshift one with a bucket and some weights, or seek assistance. You can't get good results without some way to take measurements and assess the results. This is just one small aspect of having the proper tools to allow yourself a chance at success.

I just got my Wolff Mainspring and installed it in my 625. I had a bit of trouble getting the sideplate back in place but it finally went together and the pistol worked fine so I apparently got everything back together okay. I'll load up some more full moon clips and go to the range probably tomorrow. Here's a pic of my 625-8 with a 4" barrel.

The Wolff Mainspring was a joke! It wouldn't fire either double action or single action! Finally after I tried several revolutions only one round would go off! I thought a Wolff spring would be stouter then the stock spring! Which way do I bend the mainspring to increase my hammer pressure?

If you install a Wolff power rib spring in a round butt gun you will need to use a 1/2" set screw to get enough tension on the mainspring. The combination of the rib in the spring and the change in geometry of the round butt causes this. I use a wheeler trigger pull scale and set the D/A pull at 8 pounds. Occasionally I will have to increase it to 8 1/2 pounds to get reliable ignition. It's a very quick and easy process at the range.

Try putting a piece of tin(shim) in between the strain screw and the spring. Strain screw might not be long enough to apply enough pressure

Many owners try to lighten the trigger pull by shortening the strain screw, or by unscrewing it a couple of turns. The former is legitimate so long as you don't go too far. The latter is not. A good 'lightened' trigger will yield an 8 pound DA pull and a 2 1/2 to 3 pound SA pull. But lightening the trigger pull can cause failure to ignite the primer. It is the DA pull which will suffer first.
The good news is that if you have a frame mounted firing pin, you can replace it with an extended length firing pin that will restore your reliable ignition. Apex makes a version (which I use), and there is at least one other company that does so as well. Replacement of the firing pin is pretty simple. Instructions are included.

I pulled the Wolff mainspring and I'm replacing the original spring. It's a lot stiffer then the Wolff. However I'm having trouble inserting the spent primer the other posters recommended to increase my hammer drop weight.

On the round butt guns the spent primer is a tight fit until the mainspring is tensioned a bit. I used a piece of wood to wedge the spring back a bit to get the primer inserted.

There's nothing wrong with Wolff springs , if setup properly.

I reinstalled the factory mainspring. I tried using both a large pistol primer and a small pistol primer. Both fit inside the strain screw. Both had the anvils removed. I couldn't flex the mainspring far enough to get the primer cup between the spring and the front of the grip frame and finally gave up on this attempt. I cut a flat shim out of .018" sheet metal and placed it in between the strain screw and the mainspring. After reassembling the pistol I dry fired it both single action and double action. The pistol seemed to have a stiffer hammerfall. I took it outside and testfired it double action 5 rounds and all rounds went off the first time! Problem solved! Thanks for everyone's input!

What post #4 said -large primer-but I never removed the anvil. You have to back off on the screw to install. <screw to anvil side> It worked for me several times. Don't try to bend the spring. Glad it is fixed.

Guys, if the mainspring were the problem, then wouldn't it misfire SA and DA??

I'm wondering if the problem is with a with one of the surfaces, either on the trigger or hammer, that determines how far back the hammer is drawn in DA mode. In other words, could something be worn such the hammer is not rotating back as far as it should thereby not getting the full benefit of the mainspring?

308S