Is the main spring screw on a model 19 supposed to be screwed all the way in or is it an adjustment when doing a trigger job ?

It's meant to be screwed all the way in, to provide sufficient tension to the mainspring to insure reliable ignition. Trigger jobs involve other procedures, with minimal attention to the main spring, such as thinning and polishing.

In sum, do not loosen the mainspring screw in an attempt to improve the trigger action.

John

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- Cogito, ergo armatus sum -

Screwed all the way in.

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Mike
S&WCA #3065

John & Mike are very correct . . . the strain screw (that applies tension to the mainspring) is fitted to each individual gun at the factory to attain the correct tension setting. Fitting involves grinding the tip to the correct length so that the screw can (and should) be left tightened during normal operation.

There was . . . back in the day of serious bullseye shooters . . . a modification to the grip frame that added a set-screw and plunger . . . allowing fine tuning the strain screw during a match. Not intended for the casual shooter. See posts 7 and later in this thread.
Odd vertical hole in some vintage California custom grips

Unfortunately Photobucket blocked many critical pictures but I've attached the one from post #9 that tells . . . the rest of the story.

Russ

Attached Images

StrainScrewLock_zps39972f4b.jpg (67.1 KB, 99 views)

SA on my Model 19 is about just under 2.5 pound for competition purposes it must be no less than 2.5 pound. Is there a temporary resolve to get me through the shoot tomorrow


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You might try unscrewing the strain screw, put a used primer cup under the tip of the screw and then tighten it back down to put more pressure on the main spring?
Ed

A factory trigger return spring should give you a little heavier trigger pull.

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Richard Gillespie
FBINA 102

Many thanks, used your advice, and my S&W 19 passed the SA trigger weight test.

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A retired S&W employee told me about the spent primer strategy to prevent light primer hits.

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I like Ike.

Fooling with the strain screw wont have any real effect on the single action weight. What you need to do is either install a stronger Rebound Spring or put a small shim (maybe a .17 caliber BB) under the rebound spring inside the bore in the rebound slide. BTW, whatever you use for a shim make sure it is small enough to fall out of the bore in the rebound slide or you may end up purchasing a new Rebound Slide. Obviously I advise you spend the money for a new rebound spring and would recommend trying either 14, 15, or 16 lbs Rebound Springs.

On certain guns that I use for competition and serious Target Shooting I have made up new replacement Strain Screws that are slightly shorter to lighten the pull. I do NOT do this to the original screw (I've got replacements) and never do this on a carry gun, but for a dedicated target gun I like it. The shortened screw IS FULLY tightened. The original screw is in a plastic envelope inside the guns box with a note stating that the original must be replaced before selling (just in case I'm not around to do it).

Strain Screws are cheap and take second to replace. After getting the exact length I like, I'll round them off on the nose like the Factory does, polish and blue them. Works for me!