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Thread: S&W MP .38 with loose barrel

  1. #1
    Boolit Master

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    S&W MP .38 with loose barrel

    I bought this S&W MP circa 1923 at a gunshow and I confess I missed that the barrel was loose. It has FIVE factory repair dates and is marked to J.P.D. 1933. Its been reblued at least a few times. The action is very nice and the bore is also very nice. But I'm lost on what to do about the loose barrel. I thought maybe peening the barrel threads and using locktight, but that was only a thought. I'm open to suggestions.










  2. #2
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    This problem came up a few moons back, and I think it was Texas by God who had the same problem with the same model S&W. After lots of discussion and cures such as shims, etc., I believe that we came up with applying JB weld to the threads, turning it to top dead center, and letting it set up. I think he's still got the revolver and there haven't been any problems, but maybe he'll come along and give us his thoughts.

    DG

  3. #3
    Boolit Grand Master



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    Do not peen the barrel threads. If the front sight is top dead center and no gap is visible Loctite or JB will work well. If you can see a gap shimming or peening the barrel at the shoulder of the barrel is an option. Using light taps while rolling the barrel with a series of very light taps with a polished hammer face will raise a enough material to tighten the barrel. Using JB with a gap would work but you will be able to see the JB joint.
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    I did have the same problem.
    I picked up this Round butt M&P at a gun show a few years back. I didn’t notice the barrel being loose until later. It actually has a pinned type barrel and non pinned frame.
    I discussed it with DG and I ended up using this product from Permatex, although JB weld would have worked as well.
    We took my five year old grandson out last night for a wiener/s’mores roast in the woods.
    This gun with shot loads was on my hip just in case an unwanted guest was coiled nearby.
    It’s a very handy handgun to have around.


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  5. #5
    Boolit Mold
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    The correct way to fix the loose barrel is to set it back a turn. Cut the shoulder of the barrel in a lathe enough to bring the barrel around to about the 10 o'clock position and then with the frame in a frame vise and the barrel in a barrel vise turn the barrel up to correct sight alignment. Best take it to a gunsmith with experience turning barrels. The barrel to cylinder gap will have to be reset and the forcing cone recut. No lock tight used. S&W only used green lock tight on their aluminum frames as I remember. I was a gunsmith at a S&W warranty repair station and that's how I repaired loose barrels.

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    Well, HAL-3-Seawolf, your are correct about how it can be done by the book. However, the logic here is that few individuals own a lathe. Using an adhesive allows one to bypass the cylinder gap and forcing cone problems because when the revolver was made and the barrel turned to top dead center with the front sight exactly vertical the cylinder gap was correct. So, by using an adhesive that is unlikely to ever let go (even if you want it to!) you set the barrel back to the point where it was originally, and skip the machining and gunsmith. I own perhaps a dozen M&P/Mod.10 type revolvers, and happily none of them have loose barrels. If I had one I would use a modern adhesive to solve the problem, and I was a gunsmith for 30+ years and did own a lathe. In fact, I still do own it, but seldom use it, and have a buyer lined up to haul it away as I'm retired!

    DG

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    I question why is the barrel lose in the first place especially since it's a pinned barrel. Here's a method without doing it the correct way as mentioned. Remove the barrel. Have a small hammer with an exceptionally smooth flat face and also a very smooth anvil. You tap lightly around the shoulder, that is right at the edge and you turn the barrel in very very small increments. Do this until you got all around the shoulder. Then try it in your revolver and see where the front sight ends up. I don't mean crank it it tight, I mean snug by hand. What you want is the sight to be at about 1 o'clock. If it wasn't enough peen the should all the way around again. When you get that barrel to that 1 o'clock position then you could go ahead and put some thread locker on it and tighten the barrel so the front sight is at 12 o'clock. Check to make sure your pin hole is aligned. If not find the proper size drill bit and clean it up. If this is done correctly you can't see the hammer marks on the barrel.

  8. #8
    Boolit Master

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    I want to thank you all for the solutions. The gun is not worth the cost of having a gunsmith do this job. I do have a lathe but I've not done such a job before and don't intent on starting now. I suspect I'll settle on the adhesive approach.

    Where can I buy the correct pin punch? I've read cautions against a standard flat face punch.

    Dutch

  9. #9
    Boolit Grand Master Outpost75's Avatar
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    I'm not sure what the difference in thread specs are on older S&W pinned vs. modern non-pinned barrels, but when I worked at Ruger in the 1980s barrel threads were changed from a UNEF Class 3A which was an interference fit, to a Class 2A, which enabled hand tightening to 1:00 applying blue "service removable" LocTite 242 onto the threads during assembly, intended as both a sealant and lubricant when the barrel was torqued up top dead center conforming to a fixture. Purpose of the change was to mitigate against thread choke and to prevent penetration of chlorinated solvents into threads which caused stress corrosion cracking in stainless barrels at root of the thread.

    The green Loctite that I am familiar with was 292 "wicking", intended for application onto already assembled parts. Never used it on guns, but is in common use for Cummins and Volvo diesel fuel injectors. Also a "service removable" type.
    Last edited by Outpost75; 04-16-2023 at 08:48 PM.
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  10. #10
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    First thing I would check is the barrel to cylinder gap and move on from there. If BC gap is not crazy with barrel timed a washer could be sourced but I would bet it is probably on the other side of .006".

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    Dutch it's possible with a Dremel and the correct stone to grind a cup on the flat tip punches.

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    With it being pinned and not removed Outpost75 recommendation of a wicking Loctite would be my first choice for your application.

    https://www.amazon.com/Loctite-29031...1698139&sr=8-2
    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

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  13. #13
    Boolit Master

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    Quote Originally Posted by M-Tecs View Post
    With it being pinned and not removed Outpost75 recommendation of a wicking Loctite would be my first choice for your application.

    https://www.amazon.com/Loctite-29031...1698139&sr=8-2
    I had never heard of "wicking" Loctite! That does seem to be the easiest solution so it should be the first attempt at remedying this 100 year old Smith. Many thanks.

    Dutch

  14. #14
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    Why not peen the bbl threads..
    Done right and not a butcher job, it tightens the bbl into the frame assembly perfectly. No loctite or JB Weld needed.

    If you are overly heavy handed with the hammer and drift,,yes-you will get yourself in trouble.

    You need a drift that fits the face of the thread, Not just a common round punch.
    Use a small hammer and use it lightly.

    Begin at the start of the thread at the breech end but do not do the very first 1/4 to 1/2 turn of the thread. Leave that so the thread on the bbl picks up the frame thread easily upon assembly.

    Tap the drift lightly against the back (breech) side of the V of the thread going all the way around the thread to the shoulder,,or as close to it as you can get w/o damaging the shoulder.

    I usually do approx 1/3 of the entire thread showing, then turn the bbl in the vise slightly and do another 1/3 of it or so. Untill the entire thread is done.

    Don't over do the displacement of the threads!
    It does not take very much to take up the slack of a loose bbl.
    The threads should not look any different when you are done with this treatment. That's how little you are striking them.

    When done, I wire wheel or otherwise clean the thread surface with steel wool or scotchbrite.

    Place a little grease or favorite 'never seize' formula on the threads and run the bbl home and clock it to 12'O.

    It will require a wrench to run it in if done right. It does the job in tightening the threads up.

    I've done dozens of rifles and handguns by this method over the yrs. Never a problem.
    It is an old method to tighten up loose & fragile Winchester lever action rifle TD joint instead of using those hideous Factory set screws to bulge the bbl extension plate metal outward.

    Yes you can glue stuff together,,but ..

  15. #15
    Boolit Master

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    Peening the threads will tighten the barrel, but it will likely leave the sight out of alignment. A combination of peening the threads AND peening the shoulder should tighten the barrel while keeping the sight aligned. If only slightly loose the wicking loctite should work with the least effort(no disassembly required). Use brake cleaner on the joint a few times before applying the loctite.
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    Dutch let us know what you did, how it worked out, and how she's shooting now.

  17. #17
    Boolit Master

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    Quote Originally Posted by TD1886 View Post
    Dutch let us know what you did, how it worked out, and how she's shooting now.
    I'm waiting the arrival of the wicking loctight. I've received 2 different degreasers, one is WD-40 and the other some electrical contact cleaner. Both said "leaves no residue". So we'll see. I'll post results in this thread when I get 'er done.

    Dutch

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    Boolit Grand Master Outpost75's Avatar
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    WD-40 is not a degreaser. CRC electrical contact cleaner is what I use.
    The ENEMY is listening.
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    Keep it to yourself.

  19. #19
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    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

    "Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."
    – Amber Veal

    "The Highest form of ignorance is when your reject something you don't know anything about".
    - Wayne Dyer

  20. #20
    Boolit Grand Master Outpost75's Avatar
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    Quote Originally Posted by M-Tecs View Post
    Thanks for info. Never seen WD40 Degreaser at Napa or Tractor Supply.
    The ENEMY is listening.
    HE wants to know what YOU know.
    Keep it to yourself.

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