Just like Col Colt says, this has been a very good post to read and in my case re-read.

I've had good luck with three parts outlets:

--Numrich (Gun Parts Corp)
--Midway USA (under S&W Auto Pistols [parts that fit multiple models])
--Brownells

I just picked up a 1989-vintage 5906 (old cop's gun) with the square trigger guard and Adjustable sights. I looked in MidwayUSA's website and found many parts were on the shelf.

When I took it apart, I noticed that the recoil spring guide's spring-loaded head is able to turn. Looks like I'll buy the $22 part at MidwayUSA.

The parts are out there. Remember too that a good portion of the common parts for the 5906 (most produced 3rd Gen?) will go onto a 4000/3900/4500/6900-series.

I appreciate the long replies by the Armorers. I have detail-stripped my 4566/4003 to clean them in a hot bath of water and Dial anti-bacterial soap (it does work!). I got them back together without any trouble.

Trouble shooting and diagnosing their issues is something entirely different. I defer the 'hard' stuff to my S&W trained SoCal gunsmith (b. burris handle on the Forum).

One thing that I have learned over the years is to use the Bic pens (with the removable top) to test the firing pin and/or ensuring that the decocker/safety works (the pen flies out of the barrel under FIRE and doesn't move under SAFE/hammer drop).

I must confess that my 4003TSW's (#1 of 2) recent trip to S&W was a wonderful experience. In fact, I have sent the other 4003TSW and 'Mama Bear's' 3914 to them. The 5906 (after she's de-loused and de-horned) will go back to Springfield for her 100K mile rebuild. Now if I could just find another Ed Brown competition safety for the 9mm/40-series guns!

If you want a 5906 (the Volvo 240 of 9mms), go to Buds, Robertsons Trading Post and/or CDNN. They're going for $300-350 depending on shape. GREAT gun!!!

Just my $.02