Trigger Question

[nailer]

If the trigger pull on a DA revolver is 6 lbs, what would the SA pull be?

[ksig1869]

My guess would be around 3lbs or so. I could be wrong, I had a Taurus that was terrible I think the guy I sold it to said it was 12 or so (it was DAO though)

[GuyMontag]

You have to remember that a DA pull is compressing the hammer/striker spring as well as the trigger spring. At the end of that travel you trip the sear allowing it to fall forward.

On a SA shot, the hammer/striker is already to the rear. On trigger pull you are pulling against the trigger spring and sear engagement.

You can't just assume that the SA would be a percent of the DA pull. If for instance, the hammer spring on a DA revolver is 10 pounds, but the sear is cut to allow a light letoff the DA and SA pulls would be extremely different.

If someone can explain that better, please do.

[G21.45]

OK! On a double action trigger pull you’re pulling against the weight of the main spring (hammer) AND, to a much lesser extent, the sear spring; (trigger) however, on a single action trigger pull you’re releasing the sear over the shortest possible distance required to fire the revolver. In this context - and as long as the edges of the sear's contact area are clean and sharp - a heavier main spring actually equates to a faster, 'lock time'.

Yes, there is some sort of pretensioned mechanical relationship between the main and the sear springs. I’m not a mechanical engineer; and, I'm not going to presume to genuinely understand what it is; but, the force of the sear spring is mainly used during an SA trigger pull in order to hold the sear in engagement rather than to drive the hammer.

On a double action pull does the hammer hit with the full force of both springs behind it? I don't think so. To my mind a heavier sear spring is used in order to more quickly and surely return the trigger into position for the next DA shot. I have to imagine that any contribution made by the sear spring to the overall trigger pull weight is a great deal less than that of the main spring. Will the shooter feel any increased resistance? Sure he will; but, only on a DA trigger stroke.

On a double action pull the resistance of both springs must be overcome; however, during a single action pull these two springs actually apply two different mechanical forces in order to: hold the sear in place, drive the hammer, and fire the revolver. From the shooter’s point-of-view, any single action pull is not going to feel anywhere close to a long-throw 10-12# DA trigger. (During which time the sear does NOT become engaged.)

On a single action pull the contribution made by the sear spring is much less than when pulling the hammer all the way back to the limit of its travel before it lets go. The lock time is less; the sear becomes directly involved; the travel distance is, also, significantly reduced; and, consequently, so is the amount of energy needed to make these things happen.

If you want to test trigger pull on any pistol, cock or pretension it; and, then, used a Lyman electronic trigger pull gauge in order to determine how many pounds are required in order for the sear to, ‘break’. If you want to test the DA pull on a revolver do the same thing; and record the maximum amount of weight that’s built up immediately before the sear lets go.

(It’s not going to be the same thing. The DA pull is going to be, both, longer AND heavier. I don’t know by how much; but, physical testing is the easiest way to find out.)