Personally, if the J-frame is being used for dedicated defensive carry, I won't start changing springs. Not even the rebound slide spring.
I let the former (ret) revolver armorer talk me into trying some of the different lighter weight aftermarket rebound slide springs in a new J-frame some years ago. The manufacturer from whom I ordered the springs was pretty up front in telling me that they had competitive shooters in mind with the lighter weight springs, and that I should test whatever gun they were used in to make sure of functioning.
After the armorer had gone through the gun and checked tolerances, removed some burrs and generally cleaned things up a bit, we started trying the lighter weight rebound springs.
The lightest of the pack wouldn't allow the trigger to recovery most of the time. Okay, not that one.
The "middle" spring would allow trigger recovery
almost all of the time, but it was sluggish and weak. Not that one, either.
The heaviest of the lighter weight springs allowed for consistent trigger recovery which felt decent. Lighter force in the trigger recovery (return), but also a bit lighter trigger pull. The armorer was happy. It stayed in the gun.
After I'd put a lot of rounds down range in the following months, though, I started to notice that during rapid shot strings my finger started feeling as though it was "outrunning" the trigger's recovery. I was prepped to press the trigger again before it had fully recovered. That felt weird. Not a good thing, either. Short-stroking a revolver trigger in DA mode is not good. It bothered me.
I replaced the light spring with the factory spring and the trigger's recovery was faster and more positive. No way I could get
my finger to outrun the recovery. It's remained in the gun, and my subsequent J's have all kept their robust factory springs, as well.
Now, it's certainly not unusual for a factory or private gunsmith to lighten the springs in a revolver, especially one being run for target/competition. The downside if the gun fails to run as desired is that it may have to come back for correction. The risk of a light strike or a failed trigger recovery is lost points ... not lives.
Also, the lighter springs, especially the rebound slide spring, may function a particular gun under "ideal" conditions, but not necessarily under less than ideal conditions, like when the gun becomes dirty, fouled or some sort of contaminant(s) may have reached the inside of the frame. Things which can introduce more resistance to the movement of the parts, which means the lighter springs might not work, or maybe just not work as well as when the factory spring is in the gun.
Now, what's interesting is that the "middle" weight spring that didn't work 100% of the time in
my J ended up going into the
armorer's J. He tried it and felt it worked fine for his needs, in his gun. His choice.
As a S&W revolver armorer who sees J's in use as off-duty & secondary weapons, I prefer to leave the factory springs in the guns. I'd rather invest some time "improving" the shooter, instead of re-springing guns which might actually be used in shooting situations. Imagine trying to explain in some court proceeding why a revolver may have failed to work as designed and intended by the factory because I'd changed springs, causing the gun not to run right when it was desperately needed. Not something I care to think about doing, myself.
Naturally, if someone wants to have it done by a licensed gunsmith, or the factory, meaning folks who can are experienced in this sort of work and are willing to accept responsibility for their work ... and the owner is willing to stake their life on using what are probably considered "target/competition" springs in the gun ... that's not my business.
If someone wants to install the springs themselves, and are able to do it without damaging the gun or causing a problem, then that's also not my business.
Dry-fire and live-fire will help "wear in" both the gun and shooter in most instances, I'd think. The little DA/DAO J's do have some heavy triggers, along with smaller grips and a shorter reach.
Just some thoughts I thought I'd share.
I'm not anybody's expert at anything, though.
I do happen to like the little 5-shot guns, myself. I'd neglected an older 649 I had in the safe for some years after the trend to smaller pistols chambered in duty calibers was well underway. It wasn't until I picked up one of the then-new 642-1's that I became interested in breaking out my revolvers and dusting off my revolver skills so I could more effectively use them as off-duty weapons again.
I just picked up my 6th J-frame this year, and I'm thinking about picking up another one. I like to shoot them quite a bit, too.
While shooting has been determined to be a "perishable skill", I sort of suspect that shooting a DA/DAO revolver well is probably more taxing than some other guns.
