J-frame Trigger Job: Question on hammer main spring weight.

[KBintheSLC]

I was wondering what your results have been if you added a reduced weight hammer main spring on your S&W. I know that some folks say to only swap the rebound spring with a lighter spring, and leave the hammer spring stock for reliability. But my spring kit came with both. I did order a longer firing pin just in case, but I would prefer to avoid using it if I can still get reliable operation.

 

[Hammerdown77]

I selected "just the rebound spring", but originally I replaced both. I got two light strikes using CCI primers out of between 100 and 150 rounds. They did fire the second time, though.

However, this was enough to make me nervous about potential light strikes, and since this is a carry gun and absolutely MUST ALWAYS FIRE when I need it, I went back to the stock spring.

If you are not going to carry the gun, you can use the lighter mainspring. Quite honestly, I don't notice much difference in just changing the mainspring between the lighter one and stock. What did make the most difference was pulling the sideplate and giving the internals a thorough clean and lube, dry firing 500 times, and putting in a slightly lighter return spring.

 

[Old Fuff]

Probably a stupid question, but are you going to use your little J-frame, in any context, as a defensive weapon?

If so, it is not too bright to give up reliability for a slightly lighter double- action trigger pull. I also wouldn't depend on a longer firing pin unless there was a problem with headspace or cartridge head clearance. Should you hit a soft primer the longer pin might pierce it, and then you could have real problems.

The so-called “trigger spring” isn’t exactly that. Besides pushing the trigger forward it also has to rebound the hammer (rotate the hammer backwards after firing a cartridge so the firing pin doesn’t stick out through the breech face) and reset the cylinder stop. Using a reduced rebound slide spring with a full strength hammer spring may upset the timing, and if you tried to pull the trigger before the cylinder stop had reset the result would be a hopelessly jammed action.

You may not understand all this, but I can assure you that the company engineers do. They use the springs they do to insure that under any condition, in any environment, using any primer, the revolver will go BANG! when the trigger is pulled. There is no way you can replace or modify springs – individually or in combination – that won’t affect the reliability that is built into it now.

Admittedly, the trigger pull at a certain weight (for example, 10 to12 pounds) feels heavier in a J-frame then it does in a larger revolver. That because when you downsize the frame the lockwork becomes smaller and the trigger has less leverage to rotate the hammer backwards. Replacing springs won’t change inherent design factors.

 

[KBintheSLC]

Probably a stupid question, but are you going to use your little J-frame, in any context, as a defensive weapon?

Not a stupid question at all. It is a defensive weapon. If it was just for plinking, I would go as light as possible and not worry much about it. However, the stock trigger is excessively heavy. I smoothed it out with a little stoning work, but it didn't make the pull any lighter.

There is no way you can replace or modify springs – individually or in combination – that won’t affect the reliability that is built into it now.

I agree. I do need to reduce the trigger pull though... at least a little. Currently, firing in DA is very clumsy. A 12# trigger on a 15 oz gun makes for very poor accuracy... and this is coming from a guy who grew up on revolvers. I basically need to reduce it just enough to where it still functions, but requires a bit less force.

What did make the most difference was pulling the sideplate and giving the internals a thorough clean and lube, dry firing 500 times, and putting in a slightly lighter return spring.

I did clean/lube the internals after the stoning job. The gun has been dry fired quite a bit. Unfortunately, the pull weight did not come down much over time. Maybe I will try just the rebound spring swap like you did, and see if I can get the pull down under 10#.

 

[Hammerdown77]

The trigger weight may be the same, but is it smoother? Smooth is more important, to me at least, than light.

Fuff, I believe if you send a J-frame to the S&W Performance Center for an action job, they will put a slightly lighter rebound spring in. How much lighter I don't know, probably not much.

 

[Old Fuff]

The performance center offers various packages of "competition" and "street" jobs. The difference in purpose is obvious, and street jobs supposedly have full strength springs. There are many things they can do to slightly (and sometimes considerably) reduce pull weight without messing with the spring tensions. Also if they do any polishing it is a minimal amount. The best "pro-smiths" including the factory, depend mostly on making adjustments and retrofitting parts rather then excessive polishing or spring changing.

 

[Steve 48]

My 640 is smooth as silk and reliable too. I also had the whole trigger job done. Worth every penny!!

 

[KBintheSLC]

Also if they do any polishing it is a minimal amount.

Very true. Any stoning ought to be done with the mindset of merely polishing bearing surfaces, not that of removing metal. Also, there are a couple of spots where any stoning whatsoever can quickly ruin the hammer and sear.

Luckily, the spring swap can be undone. With polishing, you have no way to undo anything.

...

 

[VA27]

Another thing to think about. With a reduced weight rebound spring, there's a chance of 'outrunning' the trigger return in fast DA work. Ed McGivern used heavier (22lb) rebound springs in his speed record setting guns.

Use the stock springs and dry-fire a thousand times with each hand. It'll smooth out the action and build up your strength at the same time.

 

[Deaf Smith]

Leave the hammer spring alone.

Use no less than a 14lb rebound spring. Better a little heavy than a little to light a spring.

Stone the rebound slide and lightly stone the frame pin holes where the hammer and trigger rotate.

Use a cratex on a dremel to polish out the insides of the rebound slide (where the rebound spring resides.)

Stone the face of the bolt stop where it connects to the trigger.

Leave the hammer sear contact and trigger sear ALONE.

Use a round chamber stone or brownel chamber polisher to polish the insides of the cylinders chambers. Lightly use a cratex to break the edges of the chamber mouth walls.

Clean up everything with a spray cleaner like powderblast.

Use Microlon on all moving parts and a dry lube on the rest.

Reassemble and lock-tite.

Then function the trigger mechanism at least a couple of hundred times.

And yep, I've done this many a time.

Deaf

 

[KBintheSLC]

Very informative Deaf Smith. I was thinking of starting with the heaviest (15lb) rebound spring in the set, to see if I can live with it. If not, I will go no less than 14 lb. Good call on working the cylinder as well... I didn't even think about that, but it could help with extraction.