Bending Mainsprings

[2000Z-71]

So I had to take my 629 Mountain Gun back into the gunsmith who did the action job on it two years ago. I was starting to get light primer strikes when firing double action. They got more frequent and started occuring during single action fire as well.

My smith re-arched the mainspring said it did not hold its shape from when he performed the original action job. Now I'm asking myself, "Is bending a main spring really the best thing to do?" Especially on a defensive revoler? It just seams to me that with leaf springs, once it's bent, it's been weakened and will not want to hold its shape.

So am I over thinking this or not? Shoule I be replacing the mainspring with a standard Smith or possible reduced power Wolff?

Thanks in advance.

 

[OKFC05]

I'm a physicist, not a gunsmith.
From basic metallurgy, bending a spring past its elastic limit after it is tempered does cause local hardening and embrittlement.
Try a simple experiment with the straight section cut out of a coathanger: Hold it by the ends and bend it in the middle; continue to hold it by the ends and try to bend it back. What you get is a "W" when it bends on both sides of the original bend, because the original bend makes that spot harder and more brittle.

I much prefer the "bossed" reduced power mainsprings to bending the original. That way the result is predictable. A grade 8, 8-32 capscrew makes an excellent longer strain screw for tuning to exact pull weight desired.

 

[cgt4570]

I agree. Wolfe ribbed mainsprings are cheap, available in a variety of weights for target or defense, and you don't need a gunsmith to install one.

 

[Wayne M]

I'm shooting mainsprings I bent over twenty years ago with no problems. Are you certain the strain screw was tight?

 

[SW CQB 45]

or could the strain screw have been shortened, backed out and the use of harder primer ammunition.

you can place a gutted spent primer over your strain screw to give you a little more tension on the mainspring.

I was told a gutted small pistol primer will fit over the strain screw and if that is not enough, a gutted large pistol primer will fit over the small pistol primer. I have not tried it though.

 

[500 Magnum Nut]

When I check the main springs for an action job, I always tap the spring on the table flat. In time they get a permanent curve which reduces the hammer tension.
In a defensive revolver the springs should be flat when removed and factory.
There are many ways to reduce the hammer tension, from replacing, bending or grinding strips of metal away from factory springs. Some guys unscrew the strain screw out some. Anyway is fine for a range toy, but not a defensive revolver.

 

[bountyhunter]

So I had to take my 629 Mountain Gun back into the gunsmith who did the action job on it two years ago. I was starting to get light primer strikes when firing double action. They got more frequent and started occuring during single action fire as well.

My smith re-arched the mainspring said it did not hold its shape from when he performed the original action job. Now I'm asking myself, "Is bending a main spring really the best thing to do?" Especially on a defensive revoler? It just seams to me that with leaf springs, once it's bent, it's been weakened and will not want to hold its shape.

So am I over thinking this or not? Shoule I be replacing the mainspring with a standard Smith or possible reduced power Wolff?

Thanks in advance.

I think any kind of reduced power mainspring on a defense gun is a BAD idea.

I do bend the mainsprings on my sport guns. If you do a mandrel bend which spreads the bend over a larger segment of the spring, it absolutely does not harm the spring. All springs weaken over time with use, and you may need to re arch it a touch sometime if you run light springs to get light trigger pulls. No big deal, they are easy to bend.

You can use a trigger pull gauge before and after to measure DA pull so you know about how much the spring went up after the bend.

If the smith messed up your spring, he either bent it too much or bent it in a small area (ie, sharp edged the bend). Make sure the strain screw is full length.

 

[bountyhunter]

When I check the main springs for an action job, I always tap the spring on the table flat. In time they get a permanent curve which reduces the hammer tension.

I have never seen one that was dead flat not even new factory springs. They always have a litle arch to them.

 

[haggis]

If you want to modify a stock mainspring (you know, all of those you have laying around from substituting Wolff springs), it is usually always better to remove metal equally from both edges than bend the spring, especially without a jig to avoid sharp bends.

Remove metal by hand, not with power tools, and go slow enough that the spring does not get too hot. Check trigger pull frequently- you don't want to get below the 8-10 pounds that will reliably ignite most quality primers.


Buck

 

[sabre]

Frank,

Bending mainsprings is not a good idea if you want the gun to actually fire every time you pull the trigger.

Do yourself a favor and replace it......

 

[Landpimp]

gun sounds funny when dryfire........they bug me

I agree. Wolfe ribbed mainsprings are cheap, available in a variety of weights for target or defense, and you don't need a gunsmith to install one.

 

[cmj8591]

If you are using a gunsmith that is doing action jobs that involve bending the mainspring (or chopping the rebound spring) to lighten the trigger pull, he's a hack and you need to find someone who knows what they are doing to work on your guns.

 

[Nightowl]

Perhaps. But that was the way it was done before Wolf springs existed. Some springs seem much heavier than others. I have no problem cutting two coils off the trigger rebound spring if needed and will work the spring a bit with the wood wedge as well. I do not want the action to be so light that it is not 100% reliable, so I do not make them feather light. The Smith action is much heavier than necessary sometimes. I have seen factory personnel use this method, albeit in the distant past. Not against the aftermarket springs, but I tried them and did not see any advantage to the old fashioned method. I have parts available if need be, but have never needed them.

Note, with the frame mounted firing pin I would be more careful, as some of them seem to be unreliable out of the box. So, any change of springs or lightening of existing springs could be a problem.