Ok, Got a killer deal on a NIB SW340PD. I stole it at $400.00. I am going to use it as a off duty/BUG. I'd like to smooth up the trigger a little without changing any springs for reliability's sake.

A buddy of mine recommended taking the slide plate off and putting some Flits inside to hone and polish everything while dry firing. He said to give it a few hundred pulls then rinse out with gun scrubber or rubbing alcohol and lubricate with cano kroil. He said he has done it with a few of the DAO Smiths as well as a Ruger SP101.

It sounds reasonable to me, but are there any specific parts I should try to avoid? Am I crazy for even considering trying this?

I had a SEAL buddy of mine that fills all his trigger mechs in all his handguns with toothpaste while breaking them in to smooth everything out, so......................

Going to a lighter trigger rebound spring won't compromise reliability so long as you don't go too light. 14 pounds is the lightest I would go with this spring. The mainspring is the one you don't want to change.

Either flitz or toothpaste will smooth things up and help remove any factory roughness. Both contain a mild abrasive. I would try to avoid putting so much in there that it gets onto the hammer/trigger/sear engagement surfaces. The surface hardening on these parts is only a few thousandths deep and removing it will ruin them.

Since you're going to have the gun open anyway, polish the bottom, and back side of the rebound slide as well as "breaking"(translates to make sure it isn't a sharp corner) the corners. Polish the area of the frame the rebound slide rides on at the bottom of the frame. Slit a small wooden dowel and insert a folded piece of 400-600 grit sandpaper. Chuck that in a drill motor and then polish the spring tunnel in the rebound slide with it. Grease the spring before putting it back into the rebound slide. Just doing this stuff to the rebound slide can make a huge difference in smoothness.

Quoted: Going to a lighter trigger rebound spring won't compromise reliability so long as you don't go too light. 14 pounds is the lightest I would go with this spring. The mainspring is the one you don't want to change.

While going lighter than a 14 pound rebound slide spring is often a bad idea in a K-frame or larger Smith, I've found that you can reliably go much lighter in a J-frame.  I suspect that the J-frame rebound slide is shorter than its larger frame counterparts.  The factory J-frame rebound slide spring is definitely shorter in the examples that I've seen.  (As an aside, the shorter J-frame rebound slide springs work well as substitutes for reduced power rebound slide springs in the larger frames.)

I agree on the J-frame mainspring.  Actually, for the sake of relaibility, I'd go ahead and get the extra-power (9 lb) mainspring to replace the factory stock 8 lb mainspring.

BTW: I wouldn't put any abrasive inside an alloy frame like a 340.  Only polish the steel parts.