No Single Action Trigger

[llano52]

I have a new to me pre 27 model with 3.5 inch barrel from late 1955 or early 1956. It's in great condition but has a problem. The double action trigger function works fine, regardless of the orientation of the gun.

No such luck when it comes to single action function. When I hold the gun with the left side of the frame parallel to the ground, the single action pull works fine. If I hold the revolver in any other orientation, normal upright shooting position or right side of the frame parallel to the ground, the single action trigger pull fails.

With the hammer cocked, pressure on the trigger causes the trigger to fly forward and the hammer to fall about half of its normal travel. Has anyone seen this condition before? Any suggestions?

I've read that S&W no longer works on the older guns, so I'm assuming this 68 year old revolver would fall under that category. Thanks for any help, I appreciate your time.

 

[USBP SW]

I can't explain the orientation issue, perhaps the way the trigger finger is positioned but what you describe sounds like push off. Basically, the trigger pull becomes so light that the rebound slide spring is more than the weight required to pull the trigger and the trigger pushes your finger forward. If you can clock the hammer, push on the back of the hammer, if it falls, you have push off.

 

[llano52]

I cocked and pushed on the back of the hammer - it does fall. So, I have push off. How do I correct it?

 

[armorer951]

The armorers manual calls for "nominal" pressure to check for push off, which to me has always been around 8-10 pounds. This was confirmed by the instructors at the S&W armorers school. Any hammer trigger interface will push off if subjected to undue pressure. It's very easy to "quantify" the correct test pressure by using a trigger pull gauge when exerting pressure on the back of the hammer while cocked SA.

Extremely light trigger pulls can also be a telltale sign of tampering and push off issues. If you have a trigger pull gauge, check to see if the trigger pull is around 3 pounds. Anything below 2.5 pounds is an indication of possible modification, tampering, or excessive wear and tear from use.

(note: Excessive hammer or trigger sideplay can also contribute to push off)

There is a bench procedure to repair push off that works very well, as long as the bevel on the trigger and the cocking notch on the hammer are in-tact, undamaged, and unmodified. A specific sized (6" x 1/2" x 1/2") Norton India stone and correct technique are required.

Unless you are familiar with S&W's "benchtop" method of sharpening the trigger bevel, I would ask a trusted local gunsmith, if you are fortunate to have one in your area, if he would check the SA and provide an opinion concerning the integrity of the SA interface.

If you are able to do so. you might also check to see if the rebound spring currently in the gun is a factory spring with 17 coils. A lighter aftermarket spring, or a spring that has been cut can contribute to push off.
Replacing the lighter rebound spring with a full length factory spring will sometimes solve the problem, without any further intervention or modification.

Very unlikely, but this could also be a broken hammer or trigger stud. You'll have to remove the sideplate to determine for sure exactly what the issue is.


Carter

 

[llano52]

Thank you for the detailed response. I will check the things you pointed out.

 

[DETROIT]

Thank you for the detailed response. I will check the things you pointed out.

What these vids, it is a great way to understand how your revolver works and it will help you with inspection. Your problem could be a few things, the only way to know is to remove the side plate.

Smith & Wesson Revolver Project - YouTube

Also, I would not send it back to smith wesson. There are several great revolver gunsmiths.

 

[dsf]

Just a guesstimate, having the push off makes me think the trigger (SA sear) doesn't move far enough forward and out of the way when the trigger is pulled - the DA sear on the hammer may be catching on the top of the sear when it drops.

If you press the trigger and the hammer does its halfway drop, if you hold the trigger fast, stop the hammer and then press the trigger again - does it raise the hammer?

 

[llano52]

Just a guesstimate, having the push off makes me think the trigger (SA sear) doesn't move far enough forward and out of the way when the trigger is pulled - the DA sear on the hammer may be catching on the top of the sear when it drops.

If you press the trigger and the hammer does its halfway drop, if you hold the trigger fast, stop the hammer and then press the trigger again - does it raise the hammer?

I'll give that a try after reassembly.

 

[llano52]

Problem solved - single action trigger sear surface was damaged. Installed a new period correct trigger.