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Old September 30, 2012, 11:06 PM   #1
brmfan
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Need to lighten revolver trigger pull

Today I bought the Mrs a SW M&P 340 in .357 mag (1 7/8") with the Crimson Trace grips and tritium front sight. She loves it except for the stiff trigger pull. Any way to lighten it up at home or do I need a smithy?? Sorry for such a newb question but I'm not exactly a wheel gunner.
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Old September 30, 2012, 11:48 PM   #2
Jim Watson
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You can buy weaker springs at very low cost.
The gun might even fire with them. I have one J series Smith that is reliable with reduced springs and one that demands full strength.

A GOOD gunsmith will smooth and fit the working parts to reduce friction and minimize mechanical losses so he can put in proportionately softer springs without compromising ignition reliability.
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Old October 1, 2012, 04:27 AM   #3
oldandslow
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brm, 10/1/12

I have a number of SW revolvers (642, 686+,329) and also was unhappy with the stock trigger pull. Since I live 3500 miles from the nearest gunsmith I needed to figure out how to do the work myself. Since I do a fair bit of semiauto pistol-smithing I had most of the tools on hand. I ordered both Jerry Kuhnhausen's book "The SW Revolver, a Shop Manual" and an American Gunsmithing Institute (AGI) DVD on function, assembly and disassembly of SW revolvers (which was pretty good except Bob Dunlap, the gunsmith, is a pretty good sedative and will put you to sleep if you watch more than 20 minutes at a time). I did all three of my pistols and all function and shoot well with a smoother, lighter trigger pull.

As Jim mentioned above it is probably simpler to get a good gunsmith to do the work. He already has the knowledge and tools to do the job right.

best wishes- oldandslow
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Old October 1, 2012, 08:04 AM   #4
drail
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If the gun is to be used for self defense take it to a pistolsmith who does revolver work. Just lightening the springs is not what you want to do on a gun that HAS to work. Most smiths will offer two types of trigger jobs on revolvers - a "duty" tune where the action is smoothed and lightened just a little and a competition tune where they will take it down as light as possible (but it may not fire with any brand of ammo.) You want a "duty" tune. And maybe buy your wife a hand strengthening device.
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Old October 1, 2012, 09:47 AM   #5
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If you have to ask, you should not do it yourself. There are too many things that can be messed up. For instance, incorrect removal of the side plate can mar the gun. Screw heads can be damaged, etc.
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Old October 1, 2012, 12:36 PM   #6
Zhillsauditor
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Quote:
And maybe buy your wife a hand strengthening device.
This is good advice. If you can get her to squeeze a rubber ball once a day her strength will improve.

I normally change my stock springs on all my revolvers. The J-frame is a bit tricky, as the smaller the revolver the stronger the springs have to be for consistent ignition. In addition, the J-frame mainspring is a little bit harder to remove than the K/N frames' mainsprings.

However, it is not difficult to change out the mainspring, and not too difficult to change the rebound spring (there is a tool that makes it very easy). I would suggest changing the mainspring from 8.5# (standard J-frame) to 8#, and the rebound spring from 14# to 12#.

Then, take it out and shoot 100 rounds of your self defense ammunition in double action. If you have any light strikes, reinstall the original mainspring. If you have trouble with the trigger reset, replace the 12# rebound spring with a 13# spring (or 14# if necessary). It can get expensive to test, but you need to be confident in the ammunition your wife is carrying.

I would not suggest doing more than that without some serious study on the matter. It is a job for a gunsmith, but there are references available and help videos on the web that can walk you though the simpler stuff. Just be prepared to spend a lot of money fixing it if you screw up.

I have done some work on my own smiths, and have never screwed anything up that wasn't fixable. I have one revolver, a model 625, that will not reliably ignite any ammunition other than ammo with federal primers. Federal primers are the softest around. However, I rarely use it for anything but range work, and, when I use it for home defense, it has federal 185 grain hollow points loaded in them, and I've never had a light strike with them.

On the other end of the spectrum, I have a model 15 that I sometimes carry, but is usually my car gun. I've replaced the springs with wilson combat springs, and did some minor polishing, and it will shoot anything I put in it, even if the trigger isn't as smooth and light as the 625.
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Old October 2, 2012, 04:43 PM   #7
g.willikers
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How she grips the revolver has a lot to do with the perceived weight of the trigger pull.
The higher on the grip she holds it, the easier it will be to pull the trigger.
The web of her hand should completely cover and be slightly higher than the upper most part of the grip panels.
And crossing her thumbs behind the hammer and pushing forward helps, too.
Just don't use that technique with an auto loading pistol.
Probably the most important part is locking the wrists, and maintaining the grip through out the trigger pull and follow through, eliminating wobble and lost motion.
Try to find Jerry Miculek's online videos on the revolver grip.
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Old October 2, 2012, 04:57 PM   #8
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If it's going to be used for defense, take it to a gunsmith.

It's not worth the risk to save a few bucks.
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Old October 2, 2012, 06:13 PM   #9
Zhillsauditor
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Quote:
If it's going to be used for defense, take it to a gunsmith.

It's not worth the risk to save a few bucks.
Even if you take it to a gunsmith, test it with 100+ rounds of your defensive ammunition. Gunsmiths screw up too, and some gunsmiths are better than others. Don't skimp on testing a gun out with your defensive ammo of choice. It's not worth the risk to save a few bucks.
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Old October 2, 2012, 08:56 PM   #10
James K
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Here is the problem. In order to fire a primer, the firing pin needs a certain amount of momentum, which is velocity x mass. The hammer on a J frame revolver already has low mass (compared to say, the hammer on an SAA Colt), so it needs velocity to fire reliably. That comes from the spring. If you weaken the spring too much, the gun may not fire or may fire under ideal conditions but fail if cold or dirty. I don't say not to reduce the spring tension, but agree that testing is absolutely necessary and building muscle strength is also a good idea.

Jim
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Old October 2, 2012, 09:40 PM   #11
michaelcj
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Back in the day when we were all carrying wheel guns for duty this came up a lot. Changing springs or backing off the main spring tension is a big no no... especially if you are "depending" on the gun.

We settled on careful and and complete polishing of the inside frame and all the "moving parts" so that we had "mirror like" bearing surfaces. You'd be amazed at how smooth and light "feeling" you can get a J/K/L/N frame...while maintaining stock spring weight.

Suggest a good smith or armorer who has done it before...come to think of it might not be that many of us left.

MJ
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Old October 3, 2012, 12:45 PM   #12
MrBorland
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Quote:
Originally Posted by James K
Here is the problem. In order to fire a primer, the firing pin needs a certain amount of momentum, which is velocity x mass. The hammer on a J frame revolver already has low mass (compared to say, the hammer on an SAA Colt), so it needs velocity to fire reliably. That comes from the spring. If you weaken the spring too much, the gun may not fire or may fire under ideal conditions but fail if cold or dirty. I don't say not to reduce the spring tension, but agree that testing is absolutely necessary and building muscle strength is also a good idea.
The primer is ignited by the power delivered by the firing pin, not momentum. Think of a swinging hammer (high power/low momentum) and a very slow-moving tractor (low power/high momentum) acting on your car's bumper. Chances are, the hammer will dent it, whereas the semi will simply push the entire car with little damage to the bumper.

All else equal, a lighter hammer picks up speed and delivers more power. One can therefore reduce spring tension a bit without losing reliability with a lighter hammer. But...as mentioned, power from a lighter hammer is more easily robbed if the action isn't true and smooth.

At any rate, the main issue with J-frames isn't the weight of the hammer (bobbed or not), but less leverage: Springs are stiffer to deliver sufficient oompf from a shorter hammer, and the smaller trigger has less mechanical advantage available to retract the hammer. It's a double whammy that makes for a stiff pull.

To the OP, there are numerous spring kits for the J-frame, but Apex Tactical's generally get very good reviews, and they do offer a J-frame kit. I'd also suggest a gunsmith to smooth the action.
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Old October 3, 2012, 01:57 PM   #13
Onward Allusion
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For a SD revolver, unless your wife has a physical impairment, do not mess with the springs - 'smith or no 'smith.

Get some snap caps and have her dry fire until the cows come home. It'll smooth out the action (if it even needs smoothing out) and it will increase her strength. Also have her strengthen her hands/fingers with a stress-ball.
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Old October 5, 2012, 11:04 PM   #14
dahermit
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If you decide to lighten the trigger pull yourself, I have a few suggestions.
Remove the side plate and remove the mainspring, hammer, trigger return slide, and the trigger. Remove all the oil/lubricant from the parts and the inside of the frame. Coat the inside of the frame and the parts with blue layout dye. Reassemble the gun and dry fire about twenty-five times.
Disassemble the gun again, remove the parts and look for any areas that have had the layout dye rubbed off. A small area of rubbing may indicate a burr (such as just behind the trigger pivot where the cylinder stop plug is upset into the frame).
If there is a large area rubbed, under the trigger or the hammer, it can mean that they are not perpendicular to the pivots (crooked that is; a frequent condition in modern S&W's) and will need trigger or hammer shims to keep them from rubbing the frame.
Note that these conditions can increase the required trigger return spring pressure, which is a factor in the felt trigger pull weight. Also, note that lightening the trigger return spring does not affect the primer strike at all; it only affects trigger reset.
Polish the inside of the trigger return slide when you have the spring out.
I have found that if a 12 lb. trigger spring does not reset reliably, there is some drag somewhere that is causing it. I suggest buying at least two return springs (12, 13 lb.), and working with the gun until it resets reliably with the 12 lb. spring. The return spring affects the feel of the double action pull as much as the main spring.
If you change the main spring, polish the mainspring strut as long as you have the spring off.
By the way, rubbing alcohol will remove the layout dye.
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