I put a spurred 4506 hammer on my 4516-1 except now the decocker only works sometimes.Mainly if I pull the lever down while putting slight pressure on the slide.It did not do this with the bobbed hammer.I have didassembled this gun before and everything has been working fine until now when I changed hammers.I did not disassemble the drum because there was no need to and am aware not to mix up springs.could maybe the frame spring be a little weak? I am at a loss here it's just a weird situation! Any thoughts would be greatly appreciated.

While i am not a gunsmith, nor an expert on the subject, I can say that I also did the swap on my 4013 without any issues. What advise can I give you? Check the length of the rod that is connected to the hammer, and also the spring. Both of which are held in place by the grip. Also take a peek and make sure you included the black plastic (for lack of better words) nipple that rests in the hole in the grip.

Chances are the length of the rod is different. Swap that from your bobbed hammer.

Fastbolt will likley chime in and say many get lucky with parts dropping in, many will be iffy and many will not fit.

sounds to me that in order for this to work, someone knowledgeable with SW 3rd Gen, tolerances and fitting of parts will be required.

Thanks for the replies.The first thing I did is use the strut from the bobbed hammer,the one that came with the 4506 hammer was about 1-1/2" longer.I think you are right about the drop in fitment.It seems the more I operate the decocker,the more it wants to function properly so I may disassemble it again and compare the hammer hooks with the bobbed hammer hooks which I probably should have done in the first place.Whatever is causing the hangup is real minor,just gotta find out where and also have to get out my third hand again for re-assembly

The tolerance of the sear release lever's engagement surface (bottom of the "foot") against the sear nose can wear and change over time and require a new lever be fitted at some point. The worn spot results from the natural rubbing between the lever's foot and the sear nose during decocking.

I could see how a "new" hammer being installed (especially in an older gun) might result in the single action cocking notches being on the larger end of the normal tolerance, and maybe not allowing the old & worn sear release lever to push the sear nose out from under the hammer's notches enough each time to consistently decock properly. Cleanliness of the internal parts can have an influence on this, as well.

Then again, the existing sear release lever might have been rapidly approaching the point in its service life & accumulated wear where it might have started failing to consistently decock with the original hammer. No way to know without checking the decocking in the gun.

It can also depend on whether the original sear release lever was fitted on the short or generous end of the recommended tolerance range when it was originally filed for that gun with those original parts.

The older levers used to be provided with the foot being machined overly long, to make up for the looser tolerances in the older guns. The newer levers are being provided made much closer to the existing tolerances of the newer CNC-produced guns & MIM parts, and yet still able to be fitted to older guns.

Since the lever is fitted by filing on the bottom of the foot, maintaining the original angle of the foot set by the factory, it usually means less filing with the newer parts. This is good because it also means a fewer number of times the pistol has to be reassembled and checked for timing tolerance between disassembling the frame enough to remove the lever and make another 1-2 file strokes on the lever's foot before reassembling it again to check timing.

The "timing" used to be checked by careful and slow manipulation of the left manual safety lever during decocking, and "gauging" the point where the hammer dropped by eyeball and snapping the hammer to see if the lever completed its downward movement after a couple of hammer snaps/impacts, as well as by whether the rear edge of the lever had reached/entered the red dot painted in the frame. (Spurless hammers had top serrations at that time and could be grasped with the edge of a wooden armorer's wedge to perform the hammer snap, or, the #4 S&W cup-end pin punch could be used as a rough gauge to check timing.)

Nowadays, though, armorers are taught to use a set of 3 numbered metal drill bits (the non-cutting ends on the bits) as Go/No-Go gauges, positioning them at a specific spot in the recess under the manual safety lever and functioning the lever until it bottoms out against the bit to check for the desired "timing" of decocking (and whether it should even occur, depending on the gauge used).

While I have found a very few guns to accept new sear release levers over the years without some filing having to be done, it's been much, much more often the case where the levers had to be fitted (filed) ... especially when an older production 3rd gen gun is involved.

While the filing itself isn't particularly a difficult task (requiring as little as a table-edge clamp vise and 6" pillar file), it does require a sure and careful hand in filing the thin cross section of the lever's foot so the proper angle is maintained ... as well as resisting making that "1 too many" file strokes about the 3rd, 4th, or 5th time the gun is disassembled to remove the lever for further fitting. Having an extra 2-3 sear release levers on hand isn't a bad idea for a new armorer learning to adjust the sear release lever, at least for the first couple of times.

A gunsmith familiar with S&W TDA guns can probably do this check for you and replace/fit the lever, if necessary, as can the factory or its warranty service centers.

How mechanically inclined are you, especially when it comes to being able to maintain an angle and flat surface when filing across the edge of a thin bit of stamped steel?

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Ret LE Firearms inst & armorer

Wow Fastbolt! Thanks for the generous information! Actually the hammer I bought was really new,never used.Bought it from Nyteman 44.It makes even more sense now that you mention not just another hammer being installed but one that is actually factory new solves the whole equation.Funny,the decocker is working like a charm now just like it did with the bobbed.Guess it realized I wasn't a three handed monkey I always enjoy reading the info that the more experienced such as yourself have to offer.That is as much fun to me as firing and cleaning the pistol honestly.Thank you sir for the great info,I have learned something new indeed.Now,about that filing straight thing-think that's better left to you armorers even though I make my living as a big rig trailer mechanic!!!

De nada.

When you installed the new hammer did you clean out any residual dried or congealed fouling around the sear, hammer and sear release lever?

I've come across the occasional pistol that exhibited decocking or hammer-follow issues, but once the gun was disassembled cleaned out normal functioning & operation was restored.

I'm sending you a PM about a "timing" check.

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Ret LE Firearms inst & armorer

Actually before I bought the gun I field stripped it in the store and the barrel/slide were spotless.looking down on the frame there was nothing but clean so I didn't think twice about the $370 I gave for it.When I got it home I took out the firing pin/drum plungers (didn't mix up the springs) and everything out of the frame I found a totally clean pistol,I was floored.Whoever owned this thing knew this pistol.It was a LE trade-in that was sitting next to a seriously abused 457 that looked like a police confiscation instead! Alot of the LE trade-ins were M&P 40's that had seen ALOT of use but this one caught my eye because of it's beauty.This thing appears to have been cared for alot and shot little since 1989.