ETA: This first comment details my original question/problem; see lower in the thread for my latest comment about the fix, including pictures and a helpful link.

Recently picked up a 4046 in excellent condition, with box and papers. A veritable unicorn here in California. Just installed new guide rod and spring and a new extractor spring as well.

Took it to the range tonight and experienced five light primer strikes--including three on the same cartridge! Winchester Ranger 180 gr FMJ new out of the box. Never before had that problem with these cartridges, over thousands of rounds across multiple guns; so I am 99.9% confident it's *not* an ammo issue.

As I tried to diagnose the issue, I dry fired the 4046 a few times and the hammer seemed (and even sounded) a bit "spongy." It did indeed seem like a light strike.

What do you think needs fixing or replacement? And, is it something I can attempt to fix on my own, or should I delegate it out to a bonafide S&W gunsmith? Thanks for your help!

The first things that pop into my mind to look at are the mainspring & the firing pin spring.

Not knowing it's history it's possible someone changed out the factory mainspring (20#) for a lighter one, to give the DAO a lighter trigger, that's problematic.

It's also possible, but I think unlikely, that (if it's) the original mainspring it could be tired & in need of replacing. Wolff Springs makes a replacement spring (#27520, type "A", long) for it.

However I think it's just as likely that the firing pin/spring tunnel needs a good cleaning. Debris & gunk can build up in it impeding free movement of them. Maybe a good cleaning (remove firing pin/spring) is all that's needed there? Wolff also sells firing pin springs (#26108 XP) separately or one is included with a replacement recoil spring (#46917) from them.

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Waiting for the break of day

Whenever one of our guys or gals started to experience light strikes in their 3rd gen's, it was usually caused by an accumulation of excessively applied solvent, CLP or oil which had migrated into the firing pin channel. It gathered fouling, and sometimes primer brass & primer cup shavings, and eventually tuned into heavy sludge and goo which interfered with the function of the spring and firing pin.

It's not common to wear out a factory mainspring.

This is why it's helpful to keep the slide pointing "muzzle down" when cleaning the breechface, so gravity helps keep fluids from running into the firing pin hole. Also, don't introduce excessive liquids to the rear of the firing pin, or the plungers, manual safety "barrel" or the disconnector cut on the bottom of the slide, as the liquid can migrate into the firing pin from those places.

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Ret LE Firearms inst & armorer

Both excellent and helpful replies, gentlemen. Thank you so much. I will do some disassembly and take a look.

Always a bit of an adventure not knowing the exact provenance or stewardship of the weapon before I owned it. It is quite possible I over lubricated/cleaned the rear of the slide and firing pin area, which may have aggravated the leftover smudge issue from previous owners.

Also have a 4006 and a 411 and have never experienced this with either of those, so I truly appreciate both of your insights and suggestions.

I'd give cleaning the firing pin and chamber a 99.9% chance of fixing it.

If you find brass shavings, they're most likely coming from the sharp edge of the firing pin hole on the breech face as the case slides across it. That can be cured by slightly--and I mean "slightly"--beveling the upper edge of the opening. That should stop any shaving.

I've used a long shanked 3/16" drill bit, fixed in a generic plastic handle (for control of pressure and short twists), to reach through the slide's muzzle bushing and lightly break the edge of the firing pin hole. Very lightly. Just enough to reflect light and bevel the sharp edge.

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Ret LE Firearms inst & armorer

Gentlemen,

Thanks again for your advice and counsel. I disassembled the firing pin/spring retainer and assembly, as recommended. When I depressed the firing pin safety/plunger, the firing pin and spring should have shot out across the table, but the pin *barely* and only partially ejected! Evidently an extremely worn spring and a firing pin chamber full of gunk, as suspected. Once I removed the firing pin, I had to extract the spring manually with a stainless pick because it was so old and rusted out.

I cleaned off the pin (which was quite dirty), vigorously cleaned out the firing pin housing with Hornady One Shot and a pipe cleaner, dried it all out, and reinstalled the pin with a new spring from Brownells.

While I have not yet taken it to the range to test it, once reassembled at home I did insert a ballpoint pen down the barrel and upon dry firing with the muzzle pointed up to my ceiling, the pen shot up and out a good foot or more. Likely fixed!

Great feeling to have the 4046 back in action! Thanks again for your help and counsel. Love this forum.

I have attached a few before/after pics for those who may be interested, and I have also included a link to a helpful YouTube video that (for newbie disassemblers like me) shows how to take apart the firing pin assembly. The portion relevant to this thread begins around :20.

Attached Images

	before-oldspring.jpg (70.6 KB, 35 views)
	pipecleaners.jpg (93.2 KB, 35 views)
	after-newspring.jpg (81.4 KB, 33 views)
	slide-before.jpg (60.8 KB, 35 views)
	slide-after2.jpg (44.7 KB, 35 views)

A couple thoughts about disassembling the slide while inspecting/cleaning the firing pin channel ...

When removing the manual safety assembly from the slide, covering the body plunger with a finger tip is a good idea. If it "pops" out (and some really do), instead of just remaining in the body's plunger hole, it can disappear to wherever it is that jumping & flying small parts go. Easier to avoid that by slipping a finger tip over the head of the plunger as it emerges from the slide, as the manual safety body is pushed out of the slide.

While the newer production guns use an ambi lever plunger that is more easily visibly distinguished than the previous plunger, the older production 3rd gen's used a different one.

The older ambi lever plunger in the 9/.40's had a semi-rounded, "shouldered" plunger head, with a flat spot on the tip, which, to a quick glance, looked similar to the (fully) round-headed "shouldered" body plunger. ("Body" means the manual safety assembly body.)

The current ambi lever plungers are virtually cylindrical, with a wide flat head. No "shoulder", like that seen below a recessed, semi-rounded head on the older style (or the body plunger). The difference in the head of the plungers meant the inside profile of the ambi levers were different, too, to accommodate the different shape of the plunger heads. The design/production "vintage" of the ambi levers & plungers need to match.

Mixing up the plungers and their springs can cause problems.

Mixing up the old style ambi lever plungers with the body plungers can create some nasty feeling manipulation of the safety/decocking lever. The flat tip of the semi-rounded lever plunger doesn't ride smoothly along the inside of the slide in the manner as does the completely rounded head of the body plunger. It drags.

Mixing up the plunger springs can make for an even nastier problem, or "surprise", though.

The ambi lever spring is made of a thinner gauge wire than the body plunger. When new & clean, it's also painted a bright blue. It can easily be compressed with light pressure between a thumb and finger.

The body plunger is a much thicker gauge wire, and heavier (and unpainted). It can't be easily compressed between thumb and finger.

If the lightly tensioned ambi lever spring were to be mistakenly used for the body plunger, the usual symptom is the manual safety assembly will "decock" itself as the slide slams to the rear under recoil and normal cycling. Momentum and inertia at work. The light ambi lever spring can't sufficiently resist the forces acting against the body plunger, and the manual safety assembly, during the sudden stop of the slide moving rearward during live-fire cycling.

When that happens, the slide will then return forward with the manual safety assembly in the On-Safe, decocked position. Obviously, when this happens, the lever will have to be lifted back to the Off-Safe/Ready-to-Fire position to make another shot. You've pretty much made yourself a single-shot pistol.

I knew an agency where this happened when a newly minted armorer made this mistake during inspecting & servicing some duty weapons. Fortunately, the mistake was later discovered during range quals, when the guns started decocking themselves and remaining On-Safe during shooting. They had, however, been carried on-duty for a short while before the mistake was discovered at the range.

BTW, a "hint" that this mistake is happening at the bench is that the heavy body plunger spring is much too stiff to be easily compressed under the ambi lever. Really stiff.

The last time one of our armorers made this mistake, it was caught and corrected when he came out (from the bench) to get me and ask me to come see what he was doing wrong ... because he couldn't get the ambi lever spring and plunger compressed enough to let him install the ambi lever. The moment I felt the tension on the ambi lever plunger, I dumped the spring and saw that it was a body plunger spring. He'd mistakenly switched the springs (but not the plungers on the older gun).

This is why I like to keep the lever & body plungers - and their springs - together, but apart from each other on the bench when I'm removing them for any armorer inspection or service. The ambi lever plunger & spring sit off to one side with the ambi lever, and the body plunger & spring sit off to the other side with the manual safety (body) assembly ... and I always take a moment to visually double-check and confirm the right plungers & springs are being reinstalled in the right holes.

Oh yeah, if "cosmetic" quality cotton-tipped swabs are used to clean/swab out the firing pin hole, make very, very sure no part of the cotton "head" is left behind. Having a "self-induced" light/no-strike condition is not a good thing. The swabs sold for gunsmithing use (with long wooden handles) hold together better than the low-cost cosmetic-type swabs.

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Ret LE Firearms inst & armorer

I use dental application cotton Q tips. They leave no wayward fuzz behind. They come with a 6 inch wooden "handle" and are perfect for gunsmithing work. Check them out on ebay. Very cheap.

Great tip! (Pun intended.) Have some sticked cotton swabs I use occasion, too, but I have noticed they do leave a bit of lint at times. Thankfully, in this case, I did NOT use them to clean out the firing pin chamber, and the pipe cleaners I have are lint-free. But thanks for the recommendation to pursue the dental grade version; I went ahead and bought a box on Amazon.