15-4 action job/spring mystery

[jeffrey]

I just got a nice nickel finish 15-4 that had a heavy, kind of gritty action. (The gun looked like it had sat unshot and unlubed in someone's sock drawer for several decades.) I took it apart, stoned some of the innards (as per Jerry Miculek's DVD), lubed it and changed out the stock mainspring for a Wolf reduced power mainspring and the stock rebound spring for a Wolf 15 lb. rebound spring.

Now the action is much smoother, but what I find puzzling is that the action is just about as heavy as before. Maybe not quite as heavy as before (I don't have a trigger pull measuring tool), but nowhere near as light as my other guns for which I have swapped out springs.

Just in case it was a matter of "strange springs," I just traded the springs between the 15-4 and a 66-5 (which feels just fine). The springs I moved from the 66-5 into the 15-4 gave me that same heavy trigger pull and the springs from the 15-4 gave me a nice light smooth trigger pull in the 66-5, so it's not the springs.

Is this simply a matter of different guns having different actions and reacting differently to the same springs? Although I am not "gunsmith," I have swapped out springs and done light stoning on maybe 10 or so of my S&W revolvers and have never encountered a problem like this before. I hope that someone can provide me some advice. Thanks!

 

[Nightowl]

Try the action with the cylinder open and then closed to see if there is any difference. The cylinder may be dragging at one or more points of contact, or just an overall tight fit.

 

[jeffrey]

Thanks for your suggestion Richard. The trigger pull seems just as heavy with the cylinder in or out. No real difference.

 

[H Richard]

How heavy of a rebound spring has it? Any signs on the sides of the trigger or hammer from dragging?

 

[500 Magnum Nut]

The strain screw has to be fit, maybe yours is longer than needed?

 

[jeffrey]

H Richard: I saw some drag lines on one side of the trigger when I first opened it up, so I stoned the trigger sides slightly. Did the same for the hammer. I replaced the stock (I assume that it was stock) rebound spring with a 15 lb. Wolf spring.

500 Magnum Nut: Oddly enough, I hadn't thought of the strain screw. I have never messed (or had to mess) with a factory screw before. Well, now that you have suggested looking at it, it seems to be the same length as the strain screw in my 19-3 square butt. When I swapped the two strain screws between the two guns, I had the same hard trigger pull in the 15-4 and the same lighter trigger pull in the 19-3; so I guess it's not a strain screw problem. (Interesting, I had never compared strain screws before and I had never noticed how much longer the strain screw is in an older, square butt K frame, as compared to a newer, round butt K frame, like my 66-5.)

Thanks for your suggestions, but the mystery persists! Should I just file down the end of the strain screw? (That seems like "cheating" and I'd much rather get to the root of the problem.)

 

[500 Magnum Nut]

H Richard: Should I just file down the end of the strain screw? (That seems like "cheating" and I'd much rather get to the root of the problem.)

How does the cylinder turn?
You might have drag in there that needs to be addressed.
Look in the FAQ, there is a way to adjust the strain screw. You hang a weight off the hammer spur and set it for that weight, (full power spring).
Just because the strain screw is the same doesn't mean it's right...

Adjust it first by backing off the screw, and lifting the gun up. It will give you an idea how much it's off.

 

[tomcatt51]

The Wolff springs should lighten the pull. Might not if the rebound spring had been cut and/or the mainspring bent to lighten the pull. Or something is dragging. The reduced power (Wolff) mainsprings sometimes cause ftf's which is fixed with a longer strain screw or different ammo/primers. The strain screw length is "fitted". I just smoothed and put springs in a 14-7, a Wolff reduced power mainspring and 12 lb rebound spring gave an 8 lb DA and 2 lb 1 oz SA pull with the stock strain screw fully tightened. Just an example. A good trigger pull gauge becomes a necessity when you start playing.

 

[jeffrey]

500 Magnum Nut: The cylinder turns just fine, doesn't bind or drag. So, I guess it is the strain screw. I should be able to go out to the range on Tuesday and see how far I can back out the strain screw without misfires (on a variety of ammo).

I assume that if I "screw up" and take too much off the strain screw, I can get another from S&W. Or is this a mistaken assumption?

Also, I am a little confused (maybe alot confused!) reading your Test Hammer Spring discussion. In this, you say to hang a weight off the hammer. In your last reply, you say to hang a weight off the trigger spur. Was this just a typo in your reply? Also, is the weight test a test for determining whether the mainspring is right rather than a test for the proper length for the strain screw? Is there something that I am missing about the relationship between the strength of the mainspring and the length of the strain screw?

Anyway, thanks alot! I really appreciate the time you have taken to think about my problem, not to mention the amazing FAQ section you have put together!

tomcatt51: I think you're right about a trigger pull gauge. Have you (or anyone else) got a suggestion for a good one?

 

[500 Magnum Nut]

I goofed up, I ment hammer and typed trigger...I fixed it. The strain screw is all the same length, and can be tuned for best trigger pull.
Check that your gun is at 3 1/4 - 3 1/2 pound. What your trying to do is see when the hammer pulls down as you lift the gun. Remember the trigger is fully depressed as you lift the gun. Take a known weight (bullets is a plastic bag work) tie it to a string, and loop the end of the string around the end of the hammer, hold trigger in and lift up the gun. If the hammer holds fast, loosen the strain screw (or file it away) and set it @ 3 1/4- 3 1/2 LBS.
Hope I make sense.

This is copied from the faq sticky:

Test Hammer Spring

First, make sure the hammer spring (main spring) is flat. Check this by removing it from the gun and laying it on the table. If it's not flat, use a rubber mallet and tap it down.
This is how I test the main spring: Always keep the strain screw tight. Then you hang weights off the hammer until the proper poundage is reached.

You file the strain screw down to adjust the poundage to at least the minimum setting. Remember, the strain screw is always fully tightened, and the side plate is on when doing this work.
Gun empty! (for 22 revolvers, put fired cases in chambers.)
Dry fire gun and hold trigger fully to rear. (The muzzle is pointed straight up while you do this test).

Cock hammer with thumb, then hook a weight around the hammer (3 1/2 LB min weight for 357. 3 ¼ LB for 38 special) I hang the weight with a piece of string looped on the end of the hammer.
The hammer must not move rearward (further back under the weight) when the gun is lifted, while the weight is attached.
The factory has heavy triggers because they don't need any accidental discharges or any extra lawsuits. Also the guns have rough spots that the heavy springs cover up. The guys putting them together don't care if it's done right or not either.

Sometimes an extra long firing pin may help with poor ignition problems. But the spring must be right too.

A "home" gun smithing way of reducing trigger pull: if you don't want to file down the screw, then using blue locktite (thread locker) back off the strain screw until the gun misfires, then go back in 1/4 turn.
Some guys cut the main spring down by removing strips (long wise) to weaken it.


With my guns, I always run full power main springs but put reduced power rebound springs to help with the double action trigger pull. This is the best way of keeping ignition yet having a lighter pull. As long the trigger resets quickly, the rebound spring is the correct one for your application.

 

[jeffrey]

500 Magnum Nut: So, am I correct in my understanding that the idea is to loosen the strain screw until the hammer moves back a bit when I raise the gun, and then to tighten the strain screw back up again so that the hammer does not move? Maybe a quarter turn after that? I would then either use blue locktite or file the screw down to that point. By being able to lift 3-1/4 lbs. without moving the hammer back, I assume that this would (normally) preclude light strikes.

 

[500 Magnum Nut]

Yes, this is in the S&Ws Armour manual. When the hammer "just" responds to the 3 1/4 - 3 1/2 LB weight then that is the position you set the screw. The lock tite is not in the book, but I added that as my suggestion, so no parts are altered. Factory guys file the screw...That's why you don't need replacement main springs.

 

[tomcatt51]

I think you're right about a trigger pull gauge. Have you (or anyone else) got a suggestion for a good one?

"Best" is probably Lyman's digital gauge but it takes some practice and a steady hand to get good reads. The "fish scales" work pretty well for giving you an idea where you're at for less money.

A hammer that will lift 3+ lbs should fire ANYTHING. I checked my 629-2 which was set up for the "old", really hard Winchester primers. It fires anything you feed it, 100% reliable. It won't quite lift 2 lbs. It has a 9 3/4 lb DA pull. Everything else is under 1 1/2 lbs "hammer lift". DA trigger pulls are from 5 to 8 lbs. They get reloads with Federal primers, but Federal factory ammo has the same primers.

 

[jeffrey]

Gentlemen: should I perform the weight test with the original factory spring or with the reduced power Wolf mainspring?

 

[tomcatt51]

Gentlemen: should I perform the weight test with the original factory spring or with the reduced power Wolf mainspring?

With the stock strain screw, the reduced power Wolff spring may not make 3 lbs. The real test is if the gun goes bang with the ammo you want to use. Usually accomplished by test firing. You can establish the least strain screw length/mainspring combination that will ignite the primers and adjust from there for the pull weight and/or margin for reliability you want. Too short a strain screw with a stock spring can create problems with the link from the hammer to spring contacting the hammer because the spring becomes "too long" because it doesn't have enough arch. It gives a "funny" stacking feel to the trigger pull when this happens.

The strain screw is 8-32 thread so 1 turn is like changing the length of the screw .031".

The "book" specs for hammer pull and rebound springs are why you get "trigger jobs" from S&W with 10+ lb DA and 3+ lb SA pulls. Keeps the corporate lawyers happy.

 

[500 Magnum Nut]

I'd set it up with the factory spring. Then see how the reduced power spring feels.

 

[jeffrey]

Thank you gentlemen! I just found out that I have to go out of town for a week and a half, so I will take your advice when I return and will report on how it all works out. Thanks again for all of your patient advice!