My wife's uncle has a 4046 (.40s&w).  The trigger pull (DA only) is atrocious and he wants fiber optic sights.  I am not a Smith guy and unsure of how their numbering system works.  I cannot find a reduced power mainspring for this model (Trapper or Wolfe) and cannot find replacement fiber optic sights (Hi-Viz,  Tru Glo) for it.  I find the parts (Brownell's) for other models but not this one.  Do these parts exist for this model?  Can I use parts for another model Smith auto in this one?  I am clueless on S&W autos, any help is appreciated greatly.

The 4046 is S&W's full-size .40 DAO, all SS construction.  I have the aluminum framed version, the 4043.  Personally, I prefer the 3rd Generation DAO Smiths over any other handgun I've ever picked up, and ended up trading my DA/SA (TDA in Smith-Speak) for their DAO counterparts.

If your uncle-in-law's (guess you can call him that) 4046 is a newer, "Tactical" model, that explains even more.  S&W changed the manufacturing process for their DAO's when they moved to the "Tactical" and "Value Line" versions and discontinued the use of seperate DAO and TDA frames and slides.  Instead of the action of the slide cocking the hammer half way on the 3rd Generations, the newer versions are only cocked one quarter of the way.  This resulted in a longer trigge pull, which feels heavier, although it really isn't.

Instead of attempting to swap out springs, you will be much better off trading the pistol for it's TDA version, the 4006.  No matter what you swap out or even if you send it out for an action job, you will never get a really light trigger pull.  A good gunsmith (like Karl Sokol at Chestnut Mountain Sports in W. Rutland, VT) can work wonders with any trigger, but all he can do is make it smoother, not considerably lighter.  If you make it too light, reliability will definately suffer.

In case you are wondering what that 4046 is really worth, here is a link to Summit Gun Brokers page with his 4046's and 4043's.  They all are in VG to Excellent shape with night sights.  The 4043 I got from him was far better than I ever expected an ex-PD gun could be:

http://www.summitgunbroker.com/974939.html

If you look for a 4006 to replace it with, you will probably be forced to spend around $400 for one.  I know where there is one for sale at a gunshop.  It's an ex-PD gun with a little wear externally, but overall, it's in good shape.  He's asking $399 for it, and that's about average for what I've seen.

Too bad it's not the 9mm all SS version, the 5946.  I'm in the market for one of those right now.

If there is anything else you need to know, just ask.  I'll do my best to help you out.  The DAO Smiths are definately not for everyone, but after owning and/or shooting almost EVERYTHING else, I have found that they simply work the best for me.  I don't like the transition of a TDA from DA to SA, and I don't like external safeties, either.  If he's got a little cash to spare on top of trading his 4046 in, he should consider checking out the S&W M&P or a Springfield Armory XD-40.  From what I've read and heard othe owners of the pistols saying, they are both outstanding pistols, with trigger pulls more like what he is looking for, I would expect.  But, don't be offended if the gunshop doesn't offer him much for the 4046.  Many shops have a lot of trouble reselling DAO's, especially full-size duty gun versions.  They do have a large enough following to deplete supplies of retailers when the price is right, but if the dealer overprices at all, they do nothing but sit on the shelves until the right person comes along.

I do have another solution to his trigger problem.  It's called a LOT of ammo!  Practice, practice and practice some more.  When you get good with the DAO Smiths, head shots on silouhettes are easy at the 50ft line.

Again, I highly recommend against swapping out any springs to lighten the trigger pull unless it's a range-only pistol.  The risk of light primer strikes would scare me if there was even a slightest chance of the pistol being used in a defensive situation.  And, it's not just how it funcitons right when the spring is installed.  As the spring wears, especially since it's partially loaded with the hammer cocked part way, it's ever so slowly being weakened.  You never know if, or when, that light primer strike could happne.  If it's at the range, no big deal.  If it's when you need it to save your life, what are you going to do then?

When it comes to the sights, check out Hi-Viz.  I don't know if they make a set for the 4046, but I hope they do, because I want my 4043 to wear a set.  I like the combination of fiber optic sights for daytime and tritium at night.  Any sight set for the 4006 (40xx Series), and probably the 5906 (59xx Series), and possibly the 6906 (69xx series) should work fine.  Beware of the model numbers of S&W.  All 3rd Generation Smiths have a 4-digit model number.  When you find a sight set advertised that you think will fit, just post a link here and I'll make sure if you want me to double check it for you.

Sorry for the long winded response.  Again, any questions, just ask!  I'm far from an expert, but I've picked up a little useless knowledge here and there!  And, make sure you let us know what he decides to do with the pistol, whether it's get used to the trigger, trade it for a TDA verison, or go with something else all together.  If he really wants a TDA, the 4006 is a proven pistol.  If he feels the all SS construction is a little heavy, have him go with the 4003 (the "3" of the last digit designates a SS slide and aluminum frame).  Even in the snappy .40 S&W, I prefer the aluminum frame.  With the ergonomics of the pistol, the recoil is still quite mild.

Thanks for the excellent reply!  I will take your advice on not swapping out springs, I have seen that lower reliability on other guns.  This one seems so heavy, I thought there might be a couple pounds to play with.  I will try the Hi-Viz sights.  Thanks again!