One thing most people do not consider is that not only do reduced power mainsprings sometimes result in mis-fires, they also affect consistency of ignition. Most believe that a primer either fires or it doesn't, this is not true. The kinetic energy with which the primer is struck has an effect on the energy released by the primer and consequently the quality of ignition of the propellant charge. Not only will mis-fires result, but also squibs.

If you don't believe this, and you have a chronograph, try this. Load a batch of ammunition which you know is close to full-power for the cartridge. Using a S&W revolver with a standard mainspring that hasn't been tinkered with.

First, shoot enough rounds to ba a statistically significant sample, at least 20, and record the results, average, extreme spread and standard deviation.

Back out the strain screw 1 turn and fire another 20 and record the results. Repeat until you start getting mis-fires.

Finally, compare results of each string. If all were done the same day, under the same conditions, you will see that as firing pin/hammer energy is reduced that average velocity will also go down, while the extreme spreads and standard deviations increase.

Believe it or not, the old saw about a gun shooting "faster" the harder the hammer strikes the cartridge really does have a basis in fact! Up to a point of course.

Do you really want to trust your life to a gun with a light mainspring just because the trigger pull is a pound or so lighter?

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Gunsmithing since 1961