The rate of the rebound slide spring has no effect on the viability of primer strikes inflicted by the hammer and mainspring.

Changing the rebound spring to a lighter, aftermarket spring will change (lighten) the trigger pull weight both in double and single action. However, if the chosen/installed rebound spring rate is too low, it will result in sluggish or incomplete trigger return which can cause reliability problems and stoppages.

Lighter rebound springs can also result in lighter single action pull rates, so be sure to verify not only the viability of the trigger return, but also measure the single action with a quality trigger pull gauge. This is especially true in J-frame models that are SA capable. As always, be sure to function check the altered action using live ammunition. S&W's recommended single action pull rate is 3 pounds.

Remember also that modification of the factory springs can effect reliability. To help mitigate potential issues, keep all firearms, especially ones used for personal protection, well maintained and clean....and the gauges within specifications, especially the rear gauge or "headspace". It may well be prudent not to modify or alter spring rates in duty or carry guns. This is a critical decision that will have to be made by each gun owner.

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Ret. LE, FA Instr, S&W Armorer