5904 Gritty, gritty trigger. Where to start?

Gentlemen, I am relatively new to the 3rd generation S&W semi-auto pistols so go easy on me.

A recent acquition, a not beat to hell 5904 has a very VERY gritty trigger. With the slide removed and the hammer cocked, just pulling the trigger the final 1/2" there is an audible grind when I pull and release the trigger (not releasing the hammer).

It feels and sounds like it it right at the top of the trigger itself (not at the rear (hammer) of the pistol), perhaps where the Drawbar meets the Drawbar Plunger? (I'm looking at an exploded diagram of the SA/DA S&W 3rd gen pistols) and that is the only thing I can see that is interacting here. It's oiled and clean.

I have a pair of 5906s to compare the trigger to, and they are not like this.

I don't want to just start ordering parts... is this common? Any suggestions?

Also, what is a good S&W armorer's manual? It looks like Stevespages.com had to remove all his S&W manuals.

Thanks in advance!

Hi, Mr. Maim!
Welcome to the Forum.

Diagnosing a gritty trigger on these pistols is tricky.

If I were you, I would begin with a complete detail strip and clean.

Then you could inspect the trigger, its pin, and the drawbar, plunger and spring.

Install these parts only in the frame and see if the grittiness is where you thought it would be.

Maybe it is.

It has been my experience that grittiness during the double action trigger pull on older S&W models like yours often results from two different problems.

The first is that the older forged hammers like yours can be roughly machined on the periphery which drags on the sear during the double action pull.

This can be reduced by stoning/smoothing this hammer arc.
S&W cured the problem by updating to the MIM hammer, which is much smoother in this critical area.

The second culprit for grittiness I've encountered was the coils of the mainspring (hammer spring) compressing/grinding into the metal spring cup in the base of the grip during the double action pull.

This can be reduced by smoothing the coils of the spring and the inside of the cup.
S&W cured the problem by updating to a plastic spring cup.

I hope this helps.

John

I agree with what John has written in the information he provided.

You might also check the cavity where the drawbar spring and plunger reside (and the plunger stem) for evidence of burrs, etc. Check the dawbar itself, make sure there are no artifacts or evidence of rubbing between the inside surface of the drawbar, and the magazines. If this is the case, there will usually be a shiny spot on the magazine shell. The outside surface of the drawbar can also rub on the frame....look for shiny rub marks.

I've also observed corrosion and oxidation in the trigger plunger cavity (inside the trigger body) which can corrupt the plunger and the spring causing resistance as the plunger cams down during the trigger's cycle rearward. Don't try to disassemble or remove the plunger....just confirm that it is working properly by checking for free movement by pushing on the top of the plunger with a 1/8" punch or similar tool. A little light lubricant here will help protect the assy from rust.


I believe John was referring to milling marks at these locations:

SA take-up:




In double action:

Excellent pictures, Armorer!

These illustrate the problems graphically.

John

Nice pics armorer.

The spots previously discussed where a rough spot on a drawbar or hammer might lend itself to a rough DA or SA trigger travel are things that suddenly became "non-issues" with MIM hammers, triggers and better machined/extruded drawbars.

The little pair of flat spots in armorer951's pic of the bottom of the hammer's tail are where the tail of the drawbar rubs up underneath the rear of the hammer during SA trigger mode. While there coincidentally is a small square jeweler's file that nicely fits in that spot (around which some crocus cloth can be tightly folded), improperly removing too much metal may risk "reducing" the angled engagement surface of the "throw notch" next to it. I'm not an engineer (nor a S&W pistol smith, or gunsmith), so I don't know what the allowable tolerances might be for making adjustments.

The introduction of nylon mainspring plungers ("hammer spring cups") and disconnectors also helped, as they were smooth and "self-lubricating" when contacting metal parts.

Another little spot that supposedly helped incrementally "smooth" the DA trigger pull was when the drawbar plunger (inside the drawbar plunger spring) was given a tapered/pointed front tip, instead of the flat tip. This was a revision which appeared sometime in the mid/late 90's. It was said that the inside of the drawbar plunger spring's coils, bumping against the edge of the plunger tip, could create some resistance as each coil might hit one or another spot of the plunger's leading square edge, as the spring was being compressed during the DA trigger pull. Maybe so, but that's a small spring, unlike the main (hammer) spring. Not sure my finger could tell the difference. In my first armorer class they told us that we could just take our 6" pillar file (or red stone) and gently round off the plunger tip, making it bullet-shaped, if we didn't want to order a new plunger (yes, it's aluminum).

A word of caution is probably merited, though. Once you remove metal, it's gone ... and S&W 3rd gen parts are getting more difficult to come by.

Mistakes on a part or an assembly that you can't easily replace may not only take your favorite gun out-of-service, but it might render it unsafe to operate. These things are usually best left to someone who has been trained and knows what they're doing, and who has preferably also acquired some careful experience in doing it correctly.

WOW! Thank you gentlemen (@JohnHL, @armorer951, and @Fastbolt) VERY MUCH for your detailed and thorough responses and armorer951 for your outstanding close-up and detailed photos!

I'll be able to work on this pistol in a couple weeks and I will definitely post back my observations before replacing or modifying any parts.

A few follow-up questions:

1) What, or where can I buy a good S&W armorer's manual or any resource that would help identify and order parts?

2) What is a good source or sources for S&W parts for the 1st-3rd generation S&W semiautomatics? Particularly the MIM hammer that each of you mentioned, and the plastic spring cup.


I really love these S&W pistols. I just won a 6906 today.

Smith & Wesson Mainspring Plunger S&W 3953TSW 4003TSW - MPN: 239020000

Mainspring Plunger : SMITH & WESSON MAINSPRING PLUNGER | Brownells

Smith & Wesson Hammer Assembly Spurred S&W 4003TSW - MPN: 262230000

Hammer Assembly, Spurred, Blue : SMITH & WESSON HAMMER ASSEMBLY, SPURRED, BLUE | Brownells

Brother jsbethel listed good sources for parts.
Brownell's and Numrich have parts schematics.

Parts can often be located on ebay or gunbroker but it can be tricky.

A good guide to disassembly and reassembly and tuning are the videos graciously provided by member BLUEBELLYYANKEE.

Here's a link:

S&W 3rd gen complete disassembly video

The link also exists in the Notable Thread Index at the top of the Semi-Auto page.

Have fun making the grit go away!

John