... a mush
trigger return that is not good. The mushiness
actually slows the DA shooting and is a great concern
for short stroking the revolver. ...
A firm and brisk DA trigger
recovery is rather important for a revolver dedicated to a self defense role.
When I bought my first 642-1, the former revolver armorer offered to install a reduced power rebound slide spring. He tried all 3 of them in the 3-pack, having me dry-fire the snub each time he tried a different spring.
The lightest consistently wouldn't allow for trigger recovery (bear in mind the action had been checked and "deburred" by the armorer, who used to build PPC revolvers).
The "middle" spring had very slow recovery.
The heaviest of the reduced power springs seemed okay. We left it in my snub and I began to shoot the dickens out of it, as it had been a few years since I'd been carrying revolvers for duty and off-duty, and I wanted to knock the rust off my revolver skills. I was also using an early 640 we had in our training vault, burning up some +P and +P+ .38SPL loads (it was the 640 marked on the frame as rated for +P+).
It wasn't long before I discovered that my returning DA revolver skills was letting my trigger finger "outrun" the DAO trigger's recovery during rapid shot strings out on the firing line. That's not good, as trying to rapidly press the trigger again before it's recovered is ... well, bad.
I replaced the reduced power rebound slide spring with the factory spring. The DAO trigger was firm and brisk in its recovery, and my trigger finger
couldn't "outrun" it in the fast and furious shot strings and qual courses-of-fire.
Now, bear in mind that my DA/DAO revolvers are all maintained pretty well, since I was subsequently trained as a S&W revolver armorer myself.
By
that I mean that if one of my S&W revolvers were to become a bit fouled inside, and the action became compromised by enough fouling, or an unexpected exposure to an environmental contaminant (dirt, sand, mud, etc), the factory spring would probably help keep the rebound slide's movement and trigger recovery firm and complete better than a lighter weight spring.
Just some thoughts. All of my S&W revolvers are only used for self defense/retirement CCW roles, so the mainsprings and rebound slide springs are factory (and relatively heavy).