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Thread: What is a strain screw?

  1. #11
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    Quote Originally Posted by grizzman View Post
    I wouldn't guarantee that the spring is at fault, but the spring is easily changed by removing the stocks. Once the stocks are removed, the strain screw can be inspected while the spring is being replaced.

    Model 19s are relatively easy to work on. Removing the grips, or even the side plate, doesn't cause tiny springs and parts to fly across the room at high velocity.

    I do recommend purchasing the correct driver bits for S&W revolvers if you think you may want to remove the side plate/cylinder/etc. They're available from Brownells.
    I will look up a couple videos online. I will look at purchasing an additional screw set just for SW revolvers. I think I have the proper bits in my "gunsmith screwdriver set," but these bits aren't marked so I could be off. I don't want to damage the gun as it's quite nice.

    I did buy it used and noticed that the grip screw is a bit messed up -looks like someone used a regular flathead before me. I will look at getting a replacement for the grip screw while I am at it. Are the grip screws the same for the square and round butt? Probably not with my luck lol. I'm also gunna have to google square vs. round butts and why the difference.

    Anyway, thanks for the ongoing help.

  2. #12
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    When you do get the screw and spring lined out and back to working, two things:
    The strain screw is always supposed to be screwed in tight.
    BLUE lock-tite is your friend.

    As mentioned before they will back out on their own with round count as will the extractor rod on the cylinder (which is left hand thread on all models after about 1950). I use a dab of BLUE on both places.

  3. #13
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    Quote Originally Posted by Hulkstr8 View Post
    Are the grip screws the same for the square and round butt?
    They are not. S&W revolver exploded drawings with part numbers are all over the internet. I suggest you look up the one that matches your revolver.

  4. #14
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    Quote Originally Posted by Hulkstr8 View Post
    I will look up a couple videos online. I will look at purchasing an additional screw set just for SW revolvers. I think I have the proper bits in my "gunsmith screwdriver set," but these bits aren't marked so I could be off. I don't want to damage the gun as it's quite nice.

    I did buy it used and noticed that the grip screw is a bit messed up -looks like someone used a regular flathead before me. I will look at getting a replacement for the grip screw while I am at it. Are the grip screws the same for the square and round butt? Probably not with my luck lol. I'm also gunna have to google square vs. round butts and why the difference.

    Anyway, thanks for the ongoing help.
    You can trim an 8-32 socket screw to length. The length (shaft, not counting the cap) should be just shy of 0.4". If your screw isn't much shorter than that and it's bottomed out then the problem isn't likely the strain screw.

    You really should just take it to a gunsmith that knows how to do normal revolver maintenance. Troubleshooting over the internet is time consuming and error prone. Because once you've got the strain screw sorted out, then you have to check the mainspring (OEM, not Wolff) and make sure the hammer-mounted firing pin isn't damaged. The -4 you've got is maybe probably an early 80s gun, so you need to determine if it uses the newer spring-loaded hammer-mounted firing pin or the non-spring-loaded kind. Offhand I don't remember when they made the change, but that impacts finding a replacement. (Also the rivets are also out of production.) Then you have to check headspace and endshake, the latter being a problem that doesn't always show up consistently if you're just going by "does the gun work or not". Etc.

    As a bonus, your gunsmith might have a proper, factory screw to replace the buggered one.

  5. #15
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    Quote Originally Posted by jh9 View Post
    You really should just take it to a gunsmith that knows how to do normal revolver maintenance. Troubleshooting over the internet is time consuming and error prone. Because once you've got the strain screw sorted out, then you have to check the mainspring (OEM, not Wolff) and make sure the hammer-mounted firing pin isn't damaged. The -4 you've got is maybe probably an early 80s gun, so you need to determine if it uses the newer spring-loaded hammer-mounted firing pin or the non-spring-loaded kind. Offhand I don't remember when they made the change, but that impacts finding a replacement. (Also the rivets are also out of production.) Then you have to check headspace and endshake, the latter being a problem that doesn't always show up consistently if you're just going by "does the gun work or not". Etc.

    As a bonus, your gunsmith might have a proper, factory screw to replace the buggered one.
    Plus 1,000,000

    Revolvers are definitely not the firearms to attempt WECSOG gunsmithing on.

  6. #16
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    Ehh, I'm still trying to find a trustworthy gunsmith in my area.

  7. #17
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    Quote Originally Posted by Hulkstr8 View Post
    Hey guys,

    I took my revolver (I'm new to revolvers) out today, SW 19-4, and had light primer strikes. Same ammo I have used before (Fiocchi 38 special) without issue. First time I've show it in the cold, but I have a hard time thinking it was the temps fault.

    I was doing some reading online and people keep talking about checking the strain screw. Like I said above, I am new to revolvers. What is a strain screw?

    Also, any other advice or tips you have for this issue lemme know. Thanks homies.
    So 1 type of ammo only? And how much of a temperature drop versus last time?

    Not a recent purchase, but had a case of Fiocchi 9mm JHP that worked fine for the first few hundred rounds, then wouldn't go bang during a GSSF match. The armorer at the match couldn't find any issues with the pistol. When I got home and tried other ammo there were no issues. The remainder of the case of Fiocchi exhibited the same deal of frequently needing more than 1 hit to fire though and in a different pistol also.
    Last edited by jsbhike; 02-11-19 at 15:09.

  8. #18
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    Quote Originally Posted by Hulkstr8 View Post
    Ehh, I'm still trying to find a trustworthy gunsmith in my area.
    http://www.glenncustom.com/pricing_revolver.html

    Then ship it off. Frank Glenn is one of the few old school revolversmiths still taking new work on a regular basis. If you ask, he might be willing to fix up your 19-4.

    I drove out to his shop when I lived in phoenix and he was very accommodating. Rates are a hell of a lot more reasonable than you'd figure for someone of his stature.

  9. #19
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    When I picked up my most recent used S&W, I also experienced light primer strikes. Tried to tighten the strain screw, but it didn't help. Opened it up at home and found the previous owner had ground off a bit of the tip of the screw and then tried to shim it with a piece of leather. A quick call to S&W customer service had a new screw in the mail to me free of charge.
    - Jeff

  10. #20
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    When we used to carry revolvers on duty, one of the "great ideas" to reduce double action trigger pull was to loosen the strain screw. BAD IDEA!! It is not an adjustment screw, it is supposed to be tightened down all the way. When the armorer told certain officers to keep them tightened all the way, some closet gunsmiths decided to removed the mainspring, bend it near the top with a little kink in it, then re-install. This also reduced the double-action pull on the trigger. HOWEVER, this resulted in even more "light hits" on the primer, and misfires.
    SO, if OP found his strain screw was cut to reduce the length, it is also possible the original spring was bent (purposely) to help reduce trigger pull by the same "gunsmith" that cut his screw. I have never seen an unaltered mainspring lose it's power and need to be replaced due to age. The original mainspring in my Model 66 (no dashes) is still good as new, as is the one in my model 15 (50 years old).

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