What was Bubba trying to do? Lighten the trigger pull????
I recently bought a used 19-3 that has had the main spring modified. It had been ground down on one side from end to end. Blued on one side and bare metal with grind marks on the other. The gun functioned perfectly with a 3 1/4 lb. trigger pull in SA. DA was off my scale but compared equally to my other model 19.
I was worried when I found Bubba's handiwork and took it to my gunsmith for a once over. I hoped the rest of internals had not been modified/damaged also. The gunsmith replaced the mainspring and strain screw and said the rest of the internals looked good. Less than $40 spent for parts, labor and peace of mind. JA
PS. I measured the SA pull with the new mainspring installed and the pull was the same as before. 3 1/4 lbs.

Hi:
Many moons ago (early 1960s) in one of the gun magazines the author described lightening the action on a S&W M27 by removing metal off both sides of the mainspring plus removing 1-2 coils off every spring. Perhaps the previous owner did this ??