1911 mainsprings

A

arkieron

New member
I have a Kimber Tactical Custom II and recently acquired a Sig 1911 carry. The Kimber trigger @4 lbs is about a pound lighter than the Commander sized Sig. I also notice that the hammer is a lot stiffer on the Sig. I wonder if Kimber uses a lighter mainspring than the Sig and if balancing that factor might bring the triggers in close?
Does anyone have information on this or do I just need to swap them and remeasure?

thanks, Ron
 
It might make a very small difference in the trigger. If you want a trigger job, your best bet is to find a 'smith who specializes in 1911's and send it to him.
 
You can affect trigger weight with a change of mainspring, but if you look at target verses combat hammers, the hammer strut pin hole is located a little differently to alter mechanical advantage. Moreover, the sear nose and hammer hook angles affect pull weight very significantly. Leaf spring finger tension alters it, too. It's an interactive exercise where you balance all these things.

If you are unfamiliar with trigger work for the 1911, I'll echo the suggestion to get it done for you. Even with a good coach, I went through three sears and two hammers before I got my tooling and technique where they needed to be to achieve a completely creep-free break at a desired weight without producing hammer fall. It's worth learning if you are into the gunsmithing, but not if your interest is as an end user.
 
Sometimes this works as a cheap substitute to a proper trigger job:

Apply forward pressure on the hammer and dry fire the gun about a dozen times. It should clean up burrs you might find on the parts. It worked on mine. Essentially all you are doing is accelerating the wear on the parts to break them in faster.

I don't believe this is dangerous but if anyone here knows better, please let me know.

- Ivan.
 
The mainspring also affects how the gun reacts in recoil, so you may want to predicate any spring changes on how the guns handle overall, rather than focusing on the pull weight. I tend not to notice the difference between a 3.5# trigger and a 5.5# trigger "after the buzzer", but do prefer the recoil impulses to be similar from one gun (of the same type) to another. 23# is standard for the mainspring, but some companies go as light as 15#. I've also found that trigger pulls lightened solely via the mainspring tend to feel mushier as they get lighter.
 
RickB +1 The mainspring needs to be heavy enough to slow the slide down when it cocks the hammer. Running a very light mainspring will mean the recoil spring is all that is controlling the slide's speed and it also will make the lock time slow enough that it is possible to move the gun off target while the hammer is falling. To properly reduce the trigger pull requires the hammer and sear angles to be mated correctly and to use enough spring to keep them together until you want them to release. Attempting to lighten the pull by playing with springs will introduce new problems.
 
What Ivan is suggesting is called "boosting" the hammer. I was taught not to polish but rather to use a #2 India stone on a sear nose so the slight roughness would allow wear room to pick up slack for any microscopic misalignment. Boosting is what we did for force that surface polishing fit into the #2's slightly rough texture.

What Rick B. said about the mainspring is correct. You don't want to over-lighten it. However, if you do need to lighten it a bit, replacing the firing pin stop with a square bottom firing pin stop will bring the hammer resistance to the slide back up by decreasing mechanical advantage of the slide against the hammer. It does this simply because the square firing pin stop cocks the hammer at a point nearer the hammer pin axis, where it has less leverage. Square firing pin stops make the slide harder to rack, as a result, but the prolonged lock time they provide also mitigates muzzle flip some, which I find helpful to accuracy and sight picture recovery.
 
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