Strain Screw

[Hairtrigger]

I just purchased a 629 Hunter second hand
I was very disappointed as it barely puts a dent in the primer. I pulled the grips and made sure the strain screw was tight. One or two out of 6 will fire. Tried different ammo. Same. I got the idea to pull the strain screw out of my 629 classic with a 5 inch barrel. I was very surprised to see there is a noticeable difference in length between the two screws.
The classic is a – five. The hunter is a – eight.

 

[series guy]

Like many others the previous owner used the strain screw to “tune” the action. When doing a proper action job the strain screw can be used for fine tuning but there is a narrow window for that. The quickest way to get your gun to shoot reliably is to install springs with a known value and an appropriate strain screw. I like to use set screws from McMaster Carr with locking compound and adjust the trigger pull using a gauge. This ensures 100 percent reliability.

 

[Shark Bait]

Start by contacting S&W and explain the issue. They might send you another screw to try, or they might ask you to send it to them to diagnose the issue.

 

[SnidelyWhiplash]

Sounds like someone filed the strain screw down too much.

 

[PatriotX]

Try a spent primer over the shorter screw end to add tension.

A new screw is also an easy option.

 

[ken158]

We hear this all the time but for new guys, you need to realize the strain screw is not designed to be an adjustment. Nothing in any S&W factory literature tells you that is it. I remember and noted in my armorers book that the class instructors commented the strain screw was a design the factory regretted making. Turning the screw in and out to get a more acceptable trigger pull to the user screws up the relationship of how the parts are designed to work. Shortening the screw and making it tight accomplishes the same thing. Now you can use a different spring and the Performance Center even uses aftermarket springs on some models but they are factory tested and proven to be reliable. In my dept when we still carried revolvers, it was a disciplinary issue if your handgun was found to be “tinkered” with by anyone that was not a factory armorer. Monthly equipment inspections and twice yearly qualifications were the norm.

 

[stang1911]

Sq. butt measures .605" OAL and .480" under the head, Rd. butt measures .505" OAL and .380" under the head. Your Welcome!

 

[stu1ritter]

We hear this all the time but for new guys, you need to realize the strain screw is not designed to be an adjustment. Nothing in any S&W factory literature tells you that is it. I remember and noted in my armorers book that the class instructors commented the strain screw was a design the factory regretted making. Turning the screw in and out to get a more acceptable trigger pull to the user screws up the relationship of how the parts are designed to work. Shortening the screw and making it tight accomplishes the same thing. Now you can use a different spring and the Performance Center even uses aftermarket springs on some models but they are factory tested and proven to be reliable. In my dept when we still carried revolvers, it was a disciplinary issue if your handgun was found to be “tinkered” with by anyone that was not a factory armorer. Monthly equipment inspections and twice yearly qualifications were the norm.

From the S&W Factory armorers manual:

 

[rct269]

Like many others the previous owner used the strain screw to “tune” the action. When doing a proper action job the strain screw can be used for fine tuning but there is a narrow window for that. The quickest way to get your gun to shoot reliably is to install springs with a known value and an appropriate strain screw. I like to use set screws from McMaster Carr with locking compound and adjust the trigger pull using a gauge. This ensures 100 percent reliability.

Want a lighter trigger pull? Just back out the strain screw. Want it lighter yet? Just keep on backing it out. You're done when nothing works any more. See how easy that was?

Ralph Tremaine

 

[Shark Bait]

I had a so-called "master gunsmith" do an action job on a 686 years ago. All that moron did was spray oil inside it and back out the strain screw. It was literally dripping oil when I picked it up. I heard the ATF shut him down not long after that. I guess he was screwing up more than action jobs.

 

[stansdds]

We here at Bubba's Skool of Kitchin Table Gunsmithin teaches tha fine art of tuning S&W trigger weights. First, we measure that tension screw, then we reinserts, then back it out till we get tha light trigger weight. Then we measure how much we backed it out and file off that amount from tha screw. Wha-la, nice, light trigger weight!

 

[JumboJVT]

The last sentence of the S&W manual page stu1ritter attached clearly says S&W sanctions filing down the screw to achieve propoer trigger pull. The definition of "proper trigger pull" is the problem here, not the adjustment method. Gun no go bangy no good.

 

[markeb]

Hairtrigger, I purchased a pack of the strain screws that Series Guy recommended several years ago. He also guided me on the install. It worked perfectly installed in my 4" 66-1. If you like, I'll send you one in the mail. Send me a PM with your address.

 

[stu1ritter]

The last sentence of the S&W manual page stu1ritter attached clearly says S&W sanctions filing down the screw to achieve propoer trigger pull. The definition of "proper trigger pull" is the problem here, not the adjustment method. Gun no go bangy no good.

This is to adjust the mainspring (hammer) weight, not so much proper trigger pull. Any S&W .38Spc/.357Mag (with a strain screw) set to these hammer weights will fire any primer made today. The trigger pull will fall where it may depending on condition of lock work parts. When this factory procedure is followed the double action trigger pull ends up being quite nice.

Stu

 

[JumboJVT]

This is to adjust the mainspring (hammer) weight, not so much proper trigger pull. Any S&W .38Spc/.357Mag (with a strain screw) set to these hammer weights will fire any primer made today. The trigger pull will fall where it may depending on condition of lock work parts. When this factory procedure is followed the double action trigger pull ends up being quite nice.

Stu

This. Don't know why I typed tigger pull. I guess using trigger weights to set the hammer fall got my fingers in front of my brain.

 

[jeffrefrig]

I bought a used 629-6, and I was very impressed with the trigger pull...until I took it out to the range. No double-action bang. At home I took off the stocks and the screw was loose about 1 1/2 turns. Works great now.

 

[SGT ROCK 11B]

I had a so-called "master gunsmith" do an action job on a 686 years ago. All that moron did was spray oil inside it and back out the strain screw. It was literally dripping oil when I picked it up. I heard the ATF shut him down not long after that. I guess he was screwing up more than action jobs.

Lots of bubbas out there.

 

[SGT ROCK 11B]

I just purchased a 629 Hunter second hand
I was very disappointed as it barely puts a dent in the primer ...

Keyword = second hand. That answered my question to start "troubleshooting".