Step One, get the S&W Shop manual by Jerry Kuhnhausen. It's widely available and an invaluable aid. I purchased mine from Brownell's but am sure that it's also available from Numrich's or Midway. At the same time I would advise you purchase a rebound slide tool, I consider it an essential and can't imagine installing a rebound spring without this tool.
BTW, the Kuhnhausen manual clearly describes how to properly remove the sideplate and this should NOT be attempted without knowing how to do it correctly. I won't describe how this is done as a further encouragement for you to get that manual. However, I will warn you that trying to remove the sideplate by prying it off will destroy the fit and cause irreperable cosmetic damage.
Step two is to install or modify the rebound spring and mainspring to reduce the tension in these areas. However, there are aspects of reducing the power of these springs that you need to be aware of.
One is the Rebound Spring. Reducing the power of this spring has a minor effect on the DA trigger pull and a major effect on the SA trigger pull. In addition, a rebound spring that is too light in a gun that hasn't been fully tuned for a very light rebound spring will cause trigger return problems that can result in the trigger not returning and locking the action up completely.
My preference for the weight of the rebound spring is 14 lbs. It functions with perfect reliability in any lockwork that is in good working order and yields a good positive trigger return. The 14 lbs. rebound spring will also result in about a 1 lbs. reduction in the DA pull and a SA pull just a tick over 3 lbs. BTW, I've experimented with a 12 lbs. rebound spring and wasn't comfortable with the sub 2 lbs. SA trigger that resulted. In addition the 12 lbs. rebound spring caused trigger return issues, a slow return on my 617 and it caused my 610 to lock up under live fire. That advice for a 14 lbs. rebound spring comes from experience.
Next up is the Mainspring tension. Adjusting this tension has the greatest returns on the DA trigger pull and almost zero effect on the SA trigger weight. It's also an area where Ignition Reliability becomes the limiting factor. Ignition primers do vary in sensitivity and the common kit's for reduced power mainsprings are sold with the warning that they will only function reliably when used with Federal Primers. If you prefer Speer Gold Dot ammunition for Defense, I would advise against installing one of these reduced power mainsprings. Speer uses CCI primers which have a reputation for being a bit hard to ignite. In addition, there have been reports that marginal ignition can cause observable effects on accuracy, basically a "weak spark" may fire the round but the resulting burn won't be as complete as it would be with a stronger primer strike.
It happens that I've recently completed some experiments with mainspring tension by using hand made shims under the head of the strain screw in combination with the factory mainspring. Doing this allowed me to adjust the mainspring tension in known fixed increments at the strain screw while keeping the strain screw full tightened. One problem with backing out the strain screw is that it can move with use, generally it will work itself looser. The gist of what I have learned is that you won't get reliable ignition with CCI primers with a DA weight under 8 lbs. without resorting to a hammer that has been lightened.
Been experimenting with the strain screw.
Cut the hammer spur off and the reduction in mass may permit reliable ignition with CCI primers at 7.5 lbs, however I have not tried doing this. Make a hammer from a bonded composite of Steel and Titanium and a DA pull of 6 lbs. or less may be feasable, however you'll need access to a high end machinist and some space age adhesives to make that super light hammer.
Bottomline, IMO an 8 lbs. double action trigger is the lower limit for a S&W revolver without taking some measures that cannot be easily reversed. If you don't ever intend to do any Single Action shooting, cutting the spur off the hammer can probably get you down to 7.5 lbs. However, my approach is somewhat conservative because currently I cannot find Federal Primers in my area and ammunition for revolvers is very much shoot what you can find. I've also found that my model 620 is stunningly accurate with Speer Lawman 125 gr. TMJ, so I've done all my testing with CCI primered ammunition. If you only shoot with Federal Primers, you can probably get another 1/2 lbs. out of the DA weight.
586 trigger pull
Linear Mode
