S&W light hammer strikes/ mainspring screw?

glockorama · January 14, 2001, 03:15 PM

I have a S&W model 28 .357 and I get an occasional light hammer strikes with various ammo. The little screw at the bottom of the mainspring is about halfway screwed in. Would tightening this screw (thereby bowing the spring more) increase the hammer fall strength? Or is it the other way around? Or does it matter?

BBBBill · January 14, 2001, 03:26 PM

Absolutely!!! That screw is supposed to be bottomed out to insure that the screw doesn't back out. Many folk do a cheap "trigger job" by backing it out a few turns, but that is totally incorrect. Even if it works for a while, it will eventually back out further rendering the gun "hors de combat." If you want a lighter trigger pull, get a smith to do a proper trigger job for you unless you have the skills/knowledge/time yourself. If you wish to pursue this yourself, ask here & some of us will talk you through it.

**4V50 Gary** · January 14, 2001, 03:59 PM

Keep that screw tight. Reliability is at issue here and the mainspring needs that screw to bear against so as to provide pressure to the hammer.

mikey357 · January 14, 2001, 04:48 PM

glockorama-the other posters have given you excellent advice! Yes, the mainspring tension screw DOES need to be "bottomed out" or screwed ALL THE WAY IN. If that results in a DA triggerpull that is too heavy, you can try one of the reduced-power mainsprings, available from Brownell's, Wolff, Wilson Combat, etc., OR you can VERY CAREFULLY reduce the length of the TIP of the mainspring tension screw-a LITTLE at a time-like, say, ten THOUSANDTHS or so...and try it for "feel" and ignition reliability. I wish I had a dollar for every used S&W revo I've seen that had the mainspring tension screw shortened TOO MUCH...I coulda' retired five years ago!!!LOL, and let us know if "bottoming out" the tension screw makes the problem "disappear"....mikey357

**Mike Irwin** · January 14, 2001, 06:59 PM

Glock,

If the mainspring strain screw backs out too far, it disables the gun. If it's half-way out right now, I'm surprised that your gun is firing at all.

Gewehr98 · January 14, 2001, 10:03 PM

OK, on the same vein...

My Steel Challenge wheelgun has developed light strikes of it's own, especially in double-action. The strain screw is all the way in, and it has a new Wolff standard weight mainspring, I even recurved it to give it some more oomph. Does anybody have numbers that reflect proper firing pin (hammer nose) protrusion for a 1941 Lend Lease 5-screw (pre-Victory Model) gun? Same lockwork was used during the conversion, it was too smooth to pass up, and not quite interchangeable with more modern Model 10's, anyway.

BBBBill · January 15, 2001, 12:48 AM

Off the top of my (bald) head, I don't remember the specs on FP protrusion. However, one thing to look for on any revo that's been "tuned" is the cylinder end shake. Sometimes this gets overlooked in the process. A gun with zero endshake just might tie up within 6 rounds if fired rapidly. Not a good thing on a duty gun. However, a gun that has a very light mainspring will missfire if there is more than a little endshake. I set endshake at .001"-.0015" on match guns. The owner knows to clean regularly to prevent buildup of lead/fouling that might tie it up. You cannot expect a light mainspring to reliably ignite the primer when it has to move the round into the cylinder (open headspace), move the cylinder forward (endshake), seat the high primer (reloading). Go ahead. Ask me how I know.

A gun setup properly will run fine with a very light trigger pull, but it does require regular attention. Endshake will open with use and can be corrected easily on S&W & Ruger revos. Colts are a bit harder to do, but I've managed those also.

radom · January 15, 2001, 01:29 AM

Yep, its the screw being loose, a shim washer does wonders at about 2 to 3 turns past where yours is at now so the screw is tight and the hammer hits hard enough to set it off.

kind of like setting the gas port setting on a FAL.

January 14, 2001, 03:59 PM	#3
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 22,306	Keep that screw tight. Reliability is at issue here and the mainspring needs that screw to bear against so as to provide pressure to the hammer. __________________ Vigilantibus et non dormientibus jura subveniunt. *Molon Labe!*

January 14, 2001, 10:03 PM	#6
Gewehr98 Senior Member Join Date: July 1, 2000 Location: Token Creek, WI Posts: 4,067	Light Strikes, Part Deux OK, on the same vein... My Steel Challenge wheelgun has developed light strikes of it's own, especially in double-action. The strain screw is all the way in, and it has a new Wolff standard weight mainspring, I even recurved it to give it some more oomph. Does anybody have numbers that reflect proper firing pin (hammer nose) protrusion for a 1941 Lend Lease 5-screw (pre-Victory Model) gun? Same lockwork was used during the conversion, it was too smooth to pass up, and not quite interchangeable with more modern Model 10's, anyway.

January 15, 2001, 01:29 AM	#8
radom Senior Member Join Date: January 21, 2000 Posts: 1,379	Yep, its the screw being loose, a shim washer does wonders at about 2 to 3 turns past where yours is at now so the screw is tight and the hammer hits hard enough to set it off.kind of like setting the gas port setting on a FAL.

January 14, 2001, 03:15 PM	#1
glockorama Senior Member Join Date: March 28, 1999 Location: WA Posts: 515	I have a S&W model 28 .357 and I get an occasional light hammer strikes with various ammo. The little screw at the bottom of the mainspring is about halfway screwed in. Would tightening this screw (thereby bowing the spring more) increase the hammer fall strength? Or is it the other way around? Or does it matter?

January 14, 2001, 03:26 PM	#2
BBBBill Senior Member Join Date: January 5, 2000 Location: Alabama Posts: 197	Absolutely!!! That screw is supposed to be bottomed out to insure that the screw doesn't back out. Many folk do a cheap "trigger job" by backing it out a few turns, but that is totally incorrect. Even if it works for a while, it will eventually back out further rendering the gun "hors de combat." If you want a lighter trigger pull, get a smith to do a proper trigger job for you unless you have the skills/knowledge/time yourself. If you wish to pursue this yourself, ask here & some of us will talk you through it.

January 14, 2001, 04:48 PM	#4
mikey357 Senior Member Join Date: November 24, 2000 Location: Griffin, GA, USA Posts: 743	glockorama-the other posters have given you excellent advice! Yes, the mainspring tension screw DOES need to be "bottomed out" or screwed ALL THE WAY IN. If that results in a DA triggerpull that is too heavy, you can try one of the reduced-power mainsprings, available from Brownell's, Wolff, Wilson Combat, etc., OR you can VERY CAREFULLY reduce the length of the TIP of the mainspring tension screw-a LITTLE at a time-like, say, ten THOUSANDTHS or so...and try it for "feel" and ignition reliability. I wish I had a dollar for every used S&W revo I've seen that had the mainspring tension screw shortened TOO MUCH...I coulda' retired five years ago!!!LOL, and let us know if "bottoming out" the tension screw makes the problem "disappear"....mikey357

January 14, 2001, 06:59 PM	#5
Mike Irwin Staff Join Date: April 14, 2000 Location: Northern Virginia Posts: 41,642	Glock, If the mainspring strain screw backs out too far, it disables the gun. If it's half-way out right now, I'm surprised that your gun is firing at all.

January 15, 2001, 12:48 AM	#7
BBBBill Senior Member Join Date: January 5, 2000 Location: Alabama Posts: 197	Off the top of my (bald) head, I don't remember the specs on FP protrusion. However, one thing to look for on any revo that's been "tuned" is the cylinder end shake. Sometimes this gets overlooked in the process. A gun with zero endshake just might tie up within 6 rounds if fired rapidly. Not a good thing on a duty gun. However, a gun that has a very light mainspring will missfire if there is more than a little endshake. I set endshake at .001"-.0015" on match guns. The owner knows to clean regularly to prevent buildup of lead/fouling that might tie it up. You cannot expect a light mainspring to reliably ignite the primer when it has to move the round into the cylinder (open headspace), move the cylinder forward (endshake), seat the high primer (reloading). Go ahead. Ask me how I know. A gun setup properly will run fine with a very light trigger pull, but it does require regular attention. Endshake will open with use and can be corrected easily on S&W & Ruger revos. Colts are a bit harder to do, but I've managed those also.