model 547 trigger reset problem

[jertex]

I just purchased a model 547 here on the forum and when I received it on Saturday, discovered that it has a trigger reset problem. Unless the trigger is released fast & hard, for lack of a better description, the trigger won't reset & the cylinder rotates but the hammer doesn't move. The trigger also feels gritty.

Video of the reset problem

I carefully removed the side-plate and didn't see any corrosion, but the rebound slide is a mess (pics below). It appears to be poorly finished from the factory. I've never seen anything like this in any of my other guns, including Dan Wessons, Rugers & even my dad's old Rossi which is basically an S&W clone. I will order a replacement today, but I smoothed & polished the existing one with 600 grit sandpaper and a qtip w/ Mother's Metal Polish, which seemed to smooth it significantly, although it didn't appear much different. This didn't help the reset at all but the gritty feel is better.

I also noticed that there is no rebound spring pin in the rebound slide and I'm wondering if this could be the problem with the reset?

Any suggestions would help. I'm pretty frustrated with this situation.

 

[armorer951]

I would guess the rebound spring is a lighter, aftermarket one, or the existing one has been cut. Replacement of the rebound slide spring with a new OEM one (or a heavier aftermarket one) will solve the reset issue. The presence or absence overtravel pin would have no effect on the reset issue.

The new rebound spring should also solve the problem of the trigger not moving forward far enough.....and the trigger bevel failing to get back under the DA sear as it should. This is what's causing the hammer to fail to move when the trigger is pulled to the rear.

A good cleaning and relubrication of the internals will help too. The gun may have been in storage/unfired for a while.

 

[jertex]

I forgot to mention that I replaced the rebound spring with a Wolff 15lb spring, which I believe is the correct spec because I thought it might be the rebound spring, and it did seem a little stiffer, but the same issue persists. Wolff springs are excellent quality, so unless it's still too light, I don't think that's the problem.

I have a 17 lb spring, so I suppose I could try that one.

 

[jertex]

I would guess the rebound spring is a lighter, aftermarket one, or the existing one has been cut. Replacement of the rebound slide spring with a new OEM one (or a heavier aftermarket one) will solve the reset issue. The presence or absence overtravel pin would have no effect on the reset issue.

The new rebound spring should also solve the problem of the trigger not moving forward far enough.....and the trigger bevel failing to get back under the DA sear as it should. This is what's causing the hammer to fail to move when the trigger is pulled to the rear.

A good cleaning and relubrication of the internals will help too. The gun may have been in storage/unfired for a while.

I think I may try the 17lb spring and see if that solves the problem. I'm going to replace the rebound slide as well because that part is just unacceptable in any gun, but especially in a quality revolver with the Smith & Wesson reputation. I'll also edit the initial post with a video of the problem that I just made, in case there are other suggestions. I've never seen a revolver do this before, but I do have limited experience.

 

[armorer951]

When the trigger is returned forward after the trigger is pulled, it's clear from the video that the trigger is either not going fully forward....or there is a problem with the hammer/DA sear.

When the trigger is fully forward, and at rest, can you manually push it further forward?

 

[jertex]

When the trigger is returned forward after the trigger is pulled, it's clear from the video that the trigger is either not going fully forward....or there is a problem with the hammer/DA sear.

When the trigger is fully forward, and at rest, can you manually push it further forward?

Yes, it it "clicks" if it didn't reset. When it resets properly, there is no movement.

 

[armorer951]

The "click" you are hearing is the DA sear in the hammer resetting. If you remove the mainspring, and the sideplate, you can carefully cycle the action by hand, and you can watch the DA sear in the hammer reset forward as the trigger moves into it's fully forward position.
There may be debris inhibiting the trigger's forward progress, or the DA sear itself may not have been fit correctly. Check for free movement of the sear also.....it has a spring behind it to that may be damaged.

 

[jertex]

I'm wondering if the side plate may be hindering the DA sear? I have to heat the frame with a hairdryer on high for 4 or 5 minutes to get the side plate back in place.

 

[armorer951]

I don't think the sideplate is the problem. You should also try compeltely assembling the action without the hammer block installed, then cycle the action to check the trigger reset. This will rule out that hammer block as causing the trigger reset issue.....which is a common problem.

 

[jertex]

I removed the hammer block since that was the simplest first step and that eliminated the problem completely.

 

[armorer951]

That's great.....I would wait until you get the new rebound slide installed before you do anything else. The installation of the new rebound may solve the issue of the hammer block without further intervention.

The problem with the existing hammer block is that it is a bit too long. Minor differences in tolerances can cause the "flag" at the top of the hammer block stem, to come in contact with the hammer in the area just under the hammer flat or hammer nose, depending on the model. This contact can cause the trigger to not fully reset.

The "fix" is to stone or file the sharp edges off of both sides of the top of the "flag" at the very top of the hammer block. This will not damage the block, or inhibit it's proper function, but allows for proper clearance as the block makes it's way up under the hammer (between hammer and frame) during the trigger return phase. I'm going to attach some photos. As I stated earlier, you should wait until the new rebound slide arrives and test after it is installed. The new reb. slide may solve the problem.


Area on the hammer block flag that needs to be relieved/removed:




Both sides of the top of the block should look like this after removal of material:

 

[jertex]

Thanks, 951, I will wait. Do you recommend I go ahead and install a rebound spring pin as well, or do some models not require this part?

 

[armorer951]

The pin is not required, and this particular model would not have been fitted with one from the factory.

 

[jertex]

Great pics, super helpful!

 

[armorer951]

You can always send me a PM if you have further issues, or if you have any problems fitting the new rebound slide to the existing hammer block.

I have some extra hammer blocks here if yours turns out to be a problem, I can send a couple for you to try.

 

[jertex]

thank you. You anticipated my next question, LOL. Is there usually much fitting required on a rebound slide?

 

[armorer951]

Actually, it should just be a "drop in". Occasionally, what's called the "hammer seat" on the top is too long (or too tall) and needs to be fit.

I've got some of the older style reb. slides here too if the prospect of installing a MIM one is a problem. One of the new production ones (MIM) should work fine though. I believe Numrich has both the new (MIM) and old style rebound slides in stock. They are all dimensionally the same for the K,L, and N frames.

 

[jertex]

I researched them last night & saw that Numrich has them. There are several on ebay as well, including some that appear to be new, old stock still in the parts pouch. I'll buy one of the original, mainly because I want to keep the gun as original as possible and I just don't like the look of the MIM parts.

The funny thing is that the company that makes the MIM parts is my customer. I automated their compound mixing process to maximize quality & efficiency. The MIM parts are actually extremely good quality and often are stronger than CNC parts, but I still don't like them, LOL.

 

[PGT]

Glad you're getting it sorted and sorry it's been a bit of a bugger to figure out.

 

[jertex]

It's just one of those things on a gun that hasn't been fired much. It's a cheap fix and I'm happy with the revolver. I went ahead and made the mod to the hammer block as 951 suggested because I wanted to make sure that would solve the problem. It worked like a charm and the revolver works like it's supposed to now. I went ahead and ordered a new, old stock rebound slide that I'll probably install at some time, but I may just leave it alone for now. It's been a great learning experience for me. I like working on guns and I suspect that others will learn from this thread if they run into a similar problem. Thanks for keeping the communication open.