I have had a good amount of 3rd gens and I am familiar with how they work. I can completely strip them down and replace parts as needed. That being said I purchased a 645. I sent it in to Novak to have it re-bead blasted and I also had the sights changed. I had Novak replace all springs in the gun while it was down. The gun came out great looking! The only spring that did not get changed was the Sear spring. So I purchased one and plan on replacing that as well. The trigger feels very "gritty" as it is pulled back. My 4506 is smooth compared to this one and feels tighter. I did clean the draw bar and used some Flitz to smooth out the sides of the draw bar a little. I am looking for some input and direction please. I understand that the trigger on 3rd gens is not going to be like a 1911, but this one is pretty bad right now. Are there other parts I should replace? Like the draw bar? Thank you in advanace

And here is the eye candy.

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You might check the cavity in the frame where the drawbar plunger and spring reside. Perhaps some burrs, or leftover media from the re-finishing/beading. Also check the movement of the trigger plunger to be sure it's not impacted, and to verify that it moves up and down freely. The top, or crown of this plunger should be smooth. There is a very stiff spring behind the plunger BTW, which should not be modified. Also, I wouldn't try to remove this spring and plunger unless there is a problem with oxidation, etc., or the spring has been corrupted or damaged by rust. Just a little light oil on the assy. will do, if needed. The oil will wick down inside the cavity.

Check the hammer stirrup for burrs. This is a stamped part, and consequently, can have nasty edges. Burrs can be stoned off the edges of the stirrup.

Check the trigger for burrs also....on the sides, where it interfaces with the frame, and on the inside of the upper surface. (hook area) You can place some Dykem or similar stain (sharpie) on the sides of the drawbar and install to check for any contact points that might be rubbing, in this area or other locations, as it moves in the frame, and interfaces with the trigger.

Also, try some very light grease on the action's contact points, like Action Lube Plus from Brownells, for instance. Don't go overboard with the lube, just a small amount on the known sites where there is a metal to metal bearing surface. It also works great on the frame rails. I believe you will feel a difference after applying this, or a similar light grease that contains molybdenum disulfide to the contact points/bearing surfaces.

Certainly not an exhaustive list, (unless you are the one doing the work) but some places to check for sure.

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Everything armorer951 says above is good advice.

However, when I encounter grittiness on the DA pull on S&W metal framed semi-auto pistols, it is almost always due to roughness on the curved front surface of the hammer where the sear drags during the trigger pull.
I see it most often on forged hammers like yours as opposed to MIM hammers which are very smooth in that area.
I think if you carefully sand or stone and smooth the curved area above the SA notches on your hammer you will notice a magnitude of improvement.

John

P.S. That sear spring pin is a bear to re-install and your sear spring is probably just fine unless it is badly rusted.

John is correct. The rough milling marks "inside the box" in the lower photo can cause "gritty" feedback in the trigger when the DA is cycled. (as the hammer rotates back) These marks can be carefully removed. Use caution not to alter the profile of the hammer, and do not go near to SA notch in the hammer.

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Thank you so much guys for the Great input. This helps a lot. I will let you know how it comes out.

Hi Armorer951 i was wondering if it would be ok to lightly polish the SA & DA notches of the Hammer just to help smooth & slip better? Just polishing no stoning or altering in anyway


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I wouldn't touch the hammer notches. Without a special fixture, the integrity of the double notch will be compromised, and the hammer will be ruined.

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armorer951 is correct.

NEVER TOUCH THE NOTCHES!

Sorry for shouting...

John

I actually purchased a MIM hammer and sear. I am going to install it and will give a report on how it feels compared to the original.

NO. Leave the edges of the notch surfaces alone. This isn't something with which the kitchen table/garage bench enthusiast ought to fool.

Going to a new style MIM hammer and MIM sear will probably help quite a bit when it comes to the DA trigger pull, for the reasons illustrated by the excellent pics in the previous thread by armorer 951. Some of those machined hammers could be very rough, depending on the sharpness of the cutters. The sear nose would drag across the roughness, and the slower you pulled, the more you felt it.

There's another spot under the rear of the hammer, behind the throw-notches, where rough machining could also be felt during the take up of the SA trigger stroke, as the tail of the drawbar dragged across them (even though it's a short surface), and that's another spot where the MIM hammers were very smooth.

Going to a soft plastic (nylon?) mainspring plunger (hammer spring cup) can also help smooth out some minor roughness during a DA trigger pull, as the soft edges of the plunger/cup wouldn't create undue "drag" as the bottom coils might touch and rub against the edge as the spring was compressed. This is a spot where some smiths used to discuss stoning, but the plastic plunger/cup was pretty friction-free by its material.

As was also mentioned by armorer951, removing (red stone) any obvious burrs on the stirrup, against which the inside of the spring coils might rub, was sometimes helpful, too.

There are some other spots that can be chaceked and dressed for burrs, but it's too easy to get carried away with stoning (or the "P" word, meaning polishing ) if you aren't familiar with what you're doing.

Stay away from trying polish things just because it might look better for edges to be polished. Dulled & worn edges on the drawbar and hammer hooks, in particular, can become the cause of functioning problems.

Replacing the sear spring typically isn't considered necessary unless the top edge has become curled (causing loss of tension), or the spring is split (lengthwise).

FWIW, there's usually a resulting minor curve to the sear pin when it's installed, so it holds the spring. It can become a bit of a pain, and frustrating, trying to hold the advancing end of the pin "down" (forward) so it meets the opposite frame hole during installation. I'm told they use a jig/fixture and press to do this nowadays.

I've done it, using punches to keep the pin under tension (and the spring from "dropping" as I installed it), as well as drift it into place, and while it worked out to be easier than I'd anticipated (being closer to a pessimist than an optimist ) , I'd just as soon not do that repair on a regular basis. In my case the gun had an aluminum alloy frame, which added a bit to my concern about the possibility of damaging the soft frame, like wallowing out and damaging the pin hole.

Just some thoughts.

Nice looking 645, BTW. Did a previous owner have the original manual safety/decocker assembly replaced with a 3rd gen assembly (meaning no more screw attachment for the ambi lever)? I don't remember whether the older slides were thinner and therefore didn't require the angled relief cut on the right side of the slide for removal of then ambi lever. The later production .45's eventually did away with needing the relief cut, as I think they made the slides a little thinner.

If you have any trouble with decocking timing, email me and I can give you the sizes of the numbered drill bits used as "gages" for checking the timing as the left lever is lowered. The fitting/filing of a new sear release lever is required to correct out-of-time decocking, though.

Also, after installing a new hammer/sear, it's necessary to check for fit with your existing drawbar. This usually includes checking for push-off in SA (done gently, to avoid actually causing a wear/damage problem to occur by exuberantly SHOVING the hammer notches over the sear nose); checking for rocking-off in DA (to check for a Skips-DA/premature DA hammer fall issue) and normal DA function (full length trigger/hammer travel and hammer release). Every once in a while a new drawbar might be required to work with a new hammer and/or sear, depending how they fit and the wear of the drawbar notches.

Congrats.

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Fastbolt - Novak mentioned that I may want to replace the sear spring. That is the only spring that didn't get replaced on the gun. I do have a new sear spring and sear pin. Should I replace the sear spring? Or leave it alone? Also I ordered a drawbar today from Numrich. I think they told me that it was new/old stock. So should I plan on installing the new drawbar, MIM hammer, MIM sear, all together? Sounds like that may be the way to go with the new parts from your nicely detailed information.

This thread prompted me to pull out and fix an old 4516-1 that had a gritty pull.
Smoothing the hammer reduced the grittiness by about half and changing the mainspring cup from metal to plastic finished the job.

Feels about the same as the 4513TSW now.

John

Did they say why they felt you might want to replace it? Is the top of the spring visibly curled or deformed?

The original sear springs were flat, and not as wide as the current spring.

The next revision was as narrow as the original, but had dimples in the middle, being a pair of vertically stacked raised dots (facing the pin). The dimples were there to help provide resistance with the presence of the sear pin, and stop the spring from dropping too low.

The current spring revision is wider than the other two, and has a thin, vertical raised ridge, or rib stamped into it. The ridge, and how it is positioned against the pin, helps prevent the spring from shifting/dropping.

I like to locate the spring so the spring tail (on the bottom), which fits into its own frame hole, is located as high/centered as possible.

I used the side of a pin punch (with flat sides on the handle) to press against the leading end of the sear pin as I installed/drifted it from one side's frame hole, across the sear spring, to the opposite side frame hole.

It was not quite a 3-handed job, without a fixture to hold the frame, as I used a blue plastic armorer's block to support the frame while I tapped the pin into the frame ... while making sure the spring didn't move ... putting pressure against the advancing pin, to give it the required amount of slight "bend" over the spring, until I got it aligned with the opposite frame hold and started into it.

There's no way to know what new/old stock really means, until you get the part and can look at it. The revised, newer drawbars have rounded corners, versus the sharply angled corners of the older bars. Also, they don't have a machined recess running up the middle of the rear of the tail, but a flat, curved surface (easier machining and no stress risers at corners). They're also a lot smoother than the older bars.

Email me and I can give you some additional pointers to check during installation.

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The mainspring cup (plunger?) that sits on the grip pin?

How does that help it feel smoother?

.

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Waiting for the break of day

The coils on the mainspring (hammer spring) can grate on the inside of the cup as the hammer is being drawn back and the spring is being compressed.

It still does it with the plastic cup, but the plastic cup is so smooth and soft (as compared to the steel cup) that you can't feel it.

John

The older metal cups could come with some rough machining. Some smiths used to remove some of the burred machining marks and smooth them out, so the outside of the spring coils didn't rub/grate against them as the spring was compressed. The plastic cups are a lot smoother and offer less resistance.

Naturally, the bottom "nub" of the cups is also softer, and frequent removal of the grip pin can cause it to wear more than the metal one. I've not yet experienced a "drifting" grip pin when the plastic up is used, though, even if it has a worn nub.

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