Smith 645 Problem

[dsf]

Today I picked up a Smith 1006, a 1076 and a 645. All like new, virtually no use. The 1006 and 1076 are fine, I'm having a SA trigger take up issue with the 645.

The DS pull is fine, clean and neat. There's no play in the trigger during DA or SA take up - the trigger retaining spring is fine. There's no problem with the trigger return spring. The SA break is fine. What's not fine is the SA take up. It's gritty as hell and I can't figure out why. It's gritty on take up and on trigger return IF I don't fully pull the trigger and make the hammer drop.

I've disassembled and checked for sharp or poorly finished surfaces on the (metal) disconnector, sear, sear spring, hammer, trigger bar and all 3 levers. Nothing obvious. The roughness is present with the slide removed so it's not any of the slide mounted plungers.

With the slide mounted and magazine inserted the SA take up is rough. With the mag removed it's smooth. The roughness goes away if (with slide removed) I depress the magazine disconnect/ejector or if I depress the disconnector. The the SA take up and reset is smooth as silk.

Any suggestions on the cause or what to check? I'm leaning towards the disconnect lever and/or disconnector, but not sure why. They both look fine.

 

[BMCM]

It's the hammer.

More specifically the radius above the full cock relief that bears against the sear as you draw back the trigger in DA.

On a carbon steel hammer that area may be stoned & polished to greatly smooth out the DA pull.

Take care to stay off the full cock relief and don't mess with the hammer notches at all.

Cheers
Bill

 

[dsf]

I don't think that's the problem, for a couple of reasons. The radius on the hammer is pretty smooth. Not polished, but close to the "good" examples shown. Also, the roughness occurs when the hammer is at full cock and during the SA trigger take up only. The trigger is moving but the hammer stays still. This seems to me to rule out the hammer face.

Additional information is that (with the slide removed, hammer cocked) when I reach down into the magwell (no mag inserted) and depress the drawbar manually then manipulate the trigger the roughness goes away. There's something about the drawbar being engaged that's causing the problem. Whether it's interaction with the ejector, the disconnector or sear I don't know. But with the trigger bar engaging the hammer, sear, etc - that's when the problem occurs.

 

[BMCM]

Seems I may have jumped to a conclusion there.

I re-read your description and with your added info it appears your drawbar is scrubbing on something when at rest. I had a similar issue a few years back that was giving me fits trying to solve... I eventually discovered the drawbar was 'sawing' on a couple spots on the frame here...

I lightly broke those sharp edges with a stone. Also polished the upper edges of the drawbar where it made contact, taking care to stay away from the hooks, and that solved the issue in my case.

I might suggest pulling the drawbar out and examining it under magnification along with inspecting the frame interior. Look for telltale signs indicating things are rubbing on stuff where they oughtn't. A jewelers loupe helps great deal. Bear in mind, sometimes it's more than one flaw that needs attention to correct a poor trigger.

Well, that's my best guess without examining the gun firsthand.

Cheers
Bill

 

[OldHack]

Could be the trigger free-play spring by the symptoms. Check out the information in this thread: 4506 how long will it last with maintenance Nice pick-ups btw!

 

[dsf]

Seems I may have jumped to a conclusion there.

I re-read your description and with your added info it appears your drawbar is scrubbing on something when at rest. I had a similar issue a few years back that was giving me fits trying to solve... I eventually discovered the drawbar was 'sawing' on a couple spots on the frame here...

I lightly broke those sharp edges with a stone. Also polished the upper edges of the drawbar where it made contact, taking care to stay away from the hooks, and that solved the issue in my case.

I might suggest pulling the drawbar out and examining it under magnification along with inspecting the frame interior. Look for telltale signs indicating things are rubbing on stuff where they oughtn't. A jewelers loupe helps great deal. Bear in mind, sometimes it's more than one flaw that needs attention to correct a poor trigger.

Well, that's my best guess without examining the gun firsthand.

Cheers
Bill

I think you're right, and thanks for the photos. The roughness occurs only during SA take up. I removed the backstrap and it's definitely the drawbar - perhaps a rough/sharp edge on it, the frame or something else it's interacting with.

 

[dsf]

I found the problem. The top rear edge of the drawbar - the "U" shaped back end of it - had very sharp edges. This part of the drawbar rides against a cut on the hammer, the final cut just behind the DA sear, and that cut was very rough. The combination caused the roughness on the SA take up. Took the edge off the drawbar, smoothed the cut on the hammer and it's cleaned up just fine. I'm guessing this is a standard move for putting a really nice action on the Smiths. Easy to do and good results.