It's a strain screw--not an adjustment screw!

[Carmoney]

There seems to be a widely-spread misconception that the way to adjust the mainspring tension on a S&W revolver is to simply back out the strain screw a few turns and call it good. About half the used guns I handle have their strain screws backed out, and there have been multiple references on this sub-forum recently indicating that shooters are loosening up their strain screws as a matter of routine.

This is a bad idea, people. Unless the strain screw is bottomed out and locked down hard, it will eventually loosen and cause misfires. I have seen several shooters first-hand (including a couple who should know better) experience this at major matches.

To lighten the mainspring tension, you can replace the spring with an aftermarket spring, bend or thin the stock spring, or shorten the strain screw (just watch out for knuckling problems if you take the latter option too far), or some combination of the above. Another option is to drill and tap the frame for a set screw to hold the strain screw in place after it's been adjusted.

In every case, when you're done, the scrain screw needs to be locked down so it can't move. Period.

[Matt Griffin]

I do like to use it for spring bending. Back it out 1/3 then start bending the spring until you get misfires. Lock down the screw and you should be safely in the no-misfire zone. But yeah, I remember starting a match without checking, and I had been messing around with the screw in practice. Nothing like shooting a course of fire with a 4-shooter.

H.

[scottyinAZ]

i wish my gun had the lock screw. i might do it now, as it has backed out twice in the last few months. i would rather have a lock screw than the other options. do you use a small allen setscrew and run it into the threads of the strain screw?? i had never adjusted the screw since i got the gun back from Randy but after thousands of trigger pulls it seems to have come loose. it turns with relative ease at this point so i marked its position and check it now. do the springs get to a point that they need to be replaced??

Scott

[Tom E]

To lighten the mainspring tension, you can replace the spring with an aftermarket spring, bend or thin the stock spring, or shorten the strain screw

In every case, when you're done, the scrain screw needs to be locked down so it can't move. Period.

Shortening the strain screw isn't using it as an adjustment? Screwing it out is somehow functionally different from shortening it? Seems to do the same thing. The important thing IS keeping it from moving in service. Stock strain screws, screwed in tight, come loose. LocTite will keep them from coming loose but you need to use the right type for the application. There's many more types than the common red and blue. 290 LocTite is made to be applied to assembled fasteners. It wicks in to the threads, will penetrate 1/2" deep. In my experience it keeps strain screws from moving, scewed in tight or not. I do use blue (242) on the yoke screw and the front sight screw. Different stuff for different applications.

[scottyinAZ]

do you apply the 290 to the spring side of the screw or the head side of the screw on the strain??

i was thinking of trying that, i dont want to pull it out as we have a big revo match sunday and i dont want to risk any problems.

Scott

[Tom E]

do you apply the 290 to the spring side of the screw or the head side of the screw on the strain??

i was thinking of trying that, i dont want to pull it out as we have a big revo match sunday and i dont want to risk any problems.

Scott

Apply it from the spring side. Doesn't take much. It will wick into threads. Does not require removing (or turning) the screw to apply.

[Carmoney]

Using loc-tite is better than nothing, I suppose. But there's always that lingering doubt about whether the screw is moving over time. Plus every time you take the gun apart (which admittedly should not be very often), I guess you'd have to count exactly how many turns it takes to remove the strain screw and then try to screw it in the same number of turns upon reassembly, right?

Hence the title of this thread. If you get the tension set so it's correct with the screw bottomed out (and I always use blue loctite even though I have the screw tightened down hard), the action will stay reliable indefinitely. And if you do have to take the gun apart and put it back together, the mainspring tension stays exactly the same when the strain screw is returned to its original tightened position.

[Tom E]

I use the strain screw to fine tune the mainspring tension. I toss the stock (garbage soft alloy) strain screw and replace them with socket set screws. I notch the head for reference for reinstalling the screw. It's plenty easy to put the screw back in in the same depth/position. Not the same no-brainer as having the stocker bottomed but being grade 8 they don't mushroom their tip where it contacts the mainspring, like the stock strain screw, becoming self shortening. You need to LocTite the stock strain screw anyway, even when it's "properly" tightened.

Edited January 2, 2009 by Tom E

[Carmoney]

Well, based on what I've seen, plenty of revolver shooters seem to be willing to accept occasional misfires. So I guess if you're one of those guys, feel free to ignore my advice! I just don't want any of my competition to have an "equipment excuse" when I whip up on them!

[Alwaystryin]

Can you give the size and thread?

I toss the stock (garbage soft alloy) strain screw and replace them with socket set screws.

[Tom E]

Can you give the size and thread?

8-32, 3/8" to 1/2" long depending. I usually shorten 1/2" ones.

[Toolguy]

I'm 100% with Carmoney on this one. I get it tuned in with the screw tightened down good and use blue Loctite. Then if

you want to work on it later, you can just unscrew without heat, but won't come loose by itself.

[Neomet]

I just don't want any of my competition to have an "equipment excuse" when I whip up on them!

Dang, you mean I could have had an excuse rather than having to admit the simple fact that you spank me like like I'm a congressman at the local S&M parlor? Bummer.....

[Carmoney]

.....but it hurts so good!!

[SharonAnne9x23]

Mr. Carmoney, what is your opinion on replacing the leaf spring with a coil spring?

[dajarrel]

There seems to be a widely-spread misconception that the way to adjust the mainspring tension on a S&W revolver is to simply back out the strain screw a few turns and call it good. About half the used guns I handle have their strain screws backed out, and there have been multiple references on this sub-forum recently indicating that shooters are loosening up their strain screws as a matter of routine.

This is a bad idea, people. Unless the strain screw is bottomed out and locked down hard, it will eventually loosen and cause misfires. I have seen several shooters first-hand (including a couple who should know better) experience this at major matches.

To lighten the mainspring tension, you can replace the spring with an aftermarket spring, bend or thin the stock spring, or shorten the strain screw (just watch out for knuckling problems if you take the latter option too far), or some combination of the above. Another option is to drill and tap the frame for a set screw to hold the strain screw in place after it's been adjusted.

In every case, when you're done, the scrain screw needs to be locked down so it can't move. Period.

I agree completely. My method is to shorten the strain screw. I back it out until it misfires, screw it back in 1/4 turn and test it. If it is reliable, I measure the amount of screw necessary to bottom it out on the shoulder and measuring carefully, (micrometer or dial indicator) remove that amount of material. Then when I apply the blue loctite, it only reinforces the friction that the shoulder of the strain screw applies to hold it in place. When I do my part, the gun is 100% reliable.

OBTW, I do most of my action work toward smoothing the action rather than manipulating springs. Smooth is good....

fwiw

dj

[David Sinko]

My match gun has a set screw installed and it works very well. If I had any of the necessary skills I'd do this to all my S&W revolvers. All the others have the screw sucked all the way in with lots of Loc-Tite. I tend to run my actions rather heavy to fire all primers and I never take the guns apart unless they have mechanical or function issues. The strain screws on all my eight or so revolvers will loosen if not secured.

Another method I have seen was done to a revolver with a grooved frontstrap. The screw slot happened to coincide with one of the grooves and the groove was punched so that it went into the screw slot and prevented the screw from turning. This is certainly not the best or most versatile way to do it, but it was very effective.

Dave Sinko

[Tom E]

Anybody noticed that there seems to be 100% agreement that a "properly" bottomed strain screw WILL NOT STAY TIGHT and "properly" bottomed unless it's LocTited? Doesn't the light come on and the thought appear that it's LocTite that keeps the strain screw from moving, not "properly" bottoming it?

[Toolguy]

Bottoming it makes it exactly repeatable. They will normally stay forever if you make them tight, the Loctite is just

insurance against Murphy's Law. Any one who is serious about winning takes all possible precautions. It sucks to

shoot a great match, but lose over some ten cent thing that could have been prevented.

[Carmoney]

Bottoming it makes it exactly repeatable. They will normally stay forever if you make them tight, the Loctite is just

insurance against Murphy's Law. Any one who is serious about winning takes all possible precautions. It sucks to

shoot a great match, but lose over some ten cent thing that could have been prevented.

That's exactly correct. If I bottom out the strain screw and tighten it down hard (i.e. as tight as I can get it without twisting the screw head off), it will never loosen up even with no loctite. I did that for years, in fact. As Toolguy says, the loctite is merely a bit of extra insurance.

[Bwana Six-Gun]

I would not presume to argue or contradict one of the great wheel-gunners in USPSA, but I have three .45 revolvers (2 625 and one priceless 25-2 6 1/2 inch) that I have not cut the screws or bent the springs, but only put Blue Loctite one the strain screw and they have yet to fail me. I thought about cutting the screws down to make them bottem out. but I had a couple of buddies who did that and still had problems.

If you Loctite them, they should hold under normal use and periodic (sp) checking.

[20nickels]

I'm was not far from shortening the screws on my revos when I read this. Since those who have gone with the harder set screws have not had problems with it eating into the mainspring, which was one of my concerns, I am going to replace the stock screw with one of those. I have borrowed an 8/32 tap and purchased two very short matching set screws today. I am going to cross drill the strain screw hole and add one of these lock screws to each side (nuke it from orbit, the only way to be sure) then loctite everything once the desired primer ignition is found. I'm sure eventually I'll start bending my own springs, so I didn't want any permanent alterations.

I did consider using a smaller lock screw (6/32?) too ensure I would not have to shorten them, biut I wanted to carry only one allen wrench If anything needed adjustments. Clear as mud? I'll post pics when I'm done. Hopefully this week, depends on my access to a drill press. If anybody can shoot holes in this please speak up, my 625 is very nervous.

[Allgoodhits]

Another with Carmoney and Toolguy. Bottom it out and tighten it very firm. I however have never used lock-tite or any thread seize compounds. But I rarely remove my strain screws.

I am not familar with the newer S&W revos, but all of my older guns can be disassembled without removing the strain screw. I simple have a wood (oak) wedge that I can insert between the inside back of the frame and the back of the flat main spring. (Today the wedge would likely be made of delrin or something. My wedge is at least 30 years old) By twisting the wedge one applies tension to the spring, this will permit me to get the hook off of the hammer do dad, then I disassemble the hammer and trigger and all that from the frame. Reverse and I can re-assemble. The main spring stays in the gun in most cases as it has enough tensioin to rest against the inside of the back strap. With this method, the strain screw is seldom removed thus stays very tight. I do check them, and have NEVER found them to have moved or loosened. The opposite is true. Since they are rarely removed, when doing do so, it can be tough. If the revo is a carry gun or house gun, definitely bottom out and tighten the strain screw.

This is old school S&W stuff, but perhaps the newer guns won't work this way with the newer hammers and triggers. It seems to me that some of the parts with the hammers today are different, but all (well most) my S&W revos are 1960 - 1985 vintage.

The wedge, ball peen hammer, file, stone and heavy lead bar or block were some of the best tools ever for S&W revos.

MJ

Edited January 4, 2009 by Allgoodhits

[revoman]

I have been using Blue Loctite since I started shooting revolvers in the 80's and I have never had one back out. Either way is a sure thing but once you cut the screw you can't add it back on but no more than they cost just order a few more for your fix it bag.

[pskys2]

1st thing never cut the original Strain Screw. If the gun works take it out and save it! If you have any problems later, like at a match it's best to immediately stick a heavier one in. I'm with Carmoney I don't want to have any problems, other than the empty space between my ears, when I storke the trigger.

Buy another, or 2 or 3... and hack away using the methods mentioned.

I've had a couple that were bottomed out and they still backed off without BLUE loctite, don't use RED, my guess is something (like dried loctite?) was crushed under the screw and loosened up as it fired.

Remember a screw backed out too far will cause the MS to knuckle and really increase, or stop, the trigger pull.