Soldering M39 rear sight base
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Thread: Soldering M39 rear sight base

  1. #1

    Default Soldering M39 rear sight base

    Hello,

    I just received an M39 in excellent exterior condition, with one major flaw--the rear sight base is loose.

    My local gunsmith suggests soft solder, but thinks that the acid etch is likely to damage surrounding finish.

    What are my options here? Is it possible to solder a rear sight base without destroying the bluing? Are there any other 'catches' with an M39 sight base that he or I need to be aware of?

  2. #2
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    Quote Originally Posted by Rivaltm View Post
    Hello,

    I just received an M39 in excellent exterior condition, with one major flaw--the rear sight base is loose.

    My local gunsmith suggests soft solder, but thinks that the acid etch is likely to damage surrounding finish.

    What are my options here? Is it possible to solder a rear sight base without destroying the bluing? Are there any other 'catches' with an M39 sight base that he or I need to be aware of?
    The sight was soft soldered from the factory and both the ring and barrel should already be tinned. Before I tried anything else, I'd just flow a little more solder in and see if that fixes it.

  3. #3
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    I agree, should not be a problem but I will offer that you have to get it hotter than you may anticipate, the entire length of the barrel will be leaching off the heat you need to get the solder to flow under that sight base.
    It even matters if you are trying to do it in an air conditioned room, best to do it outside if the temps are above your work area and in any case see if you can heat the whole thing in the oven before moving to a torch.
    My experience has been that it just takes a long time to heat it up enough to flow the solder..

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  5. #4
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    The best solution is to use an OA torch with a brazing tip. This ia far and away more efficient than mucking about with a small propane torch meant for soldering plumbing joints.

    The OA gear will heat it up quickly, which will localize the heat as much as can be hoped for.

  6. #5

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    So do you think it will need any kind of acid or flux treatment before soldering, or just go to town on it as-is? Is any oil that might have wicked its way into the joint going to be a problem?

    How likely is it for the heat to spoil the bluing?

    I'm trying to decide whether I want to tackle the project or just send the rifle back. The seller seems like a stand up guy who simply didn't notice the issue; if it's easily corrected I'm all for fixing it,but I'm not sure of all of the wrinkles to this process just yet

  7. #6
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    Heat will likely damage bluing.

    If it is still very solid but just wobbles a bit I would use JB Weld metal reinforced epoxy carefully put under it. Wipe off excess immediately with white vinegar before it sets. (Clean first with carb cleaner with the action out of the stock as carb cleaner ruins stock finishes.)

  8. #7
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    Epoxy? Why not take it to a gunsmith and pay a few dollars and have it properly repaired/restored?
    Either that or send it back and get another, few as they may be, they are still around and in some numbers yet..

  9. #8
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    Quote Originally Posted by chasdev View Post
    Epoxy? Why not take it to a gunsmith and pay a few dollars and have it properly repaired/restored?
    Either that or send it back and get another, few as they may be, they are still around and in some numbers yet..
    Home Run !! Not going to cost much to have it done right but sending back a broke dick rifle is always an option. Ruining the rifle with a half assed job is not smart.

  10. #9
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    Most likely all what needs to be done is to reheat the rear sight and just let it set and cool slowly when done - Oxyacetylene brazing tip would be ideal, but a newer single burner coleman gas stove using unleaded gas if it is set up for UL gas, has worked for me. Use soapstone on areas you don't want solder or flux(if needed) to have contact with.

    Too much heat & all the solder leaks out, not enough heat and the solder does not flow.... Good luck!

    BTW - Acid base flux eats bluing, but....the heat from soldering has not affected the bluing on the guns I have soldered/sweated sights on and yes, regular lead tin solder is all you need.

    Pahtu.

  11. #10
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    If you do solder it, a bit of non-corrosive flux will help, and also, don't play the heat directly on the sight, you need to warm the barrel and sight or the solder won't key right. I'd put barreled action in a padded vise, sight uppermost, tinned if needs be, then place sight exactly where you want it and run a wire over the sight, with a heavy weight suspended on it, so as the solder melts, the weight will cause the sight so settle down on to the barrel. as soon as sight is properly settled, remove heat.

    Good luck.
    R.

  12. #11

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    Quote Originally Posted by Pahtu View Post
    Most likely all what needs to be done is to reheat the rear sight and just let it set and cool slowly when done - Oxyacetylene brazing tip would be ideal, but a newer single burner coleman gas stove using unleaded gas if it is set up for UL gas, has worked for me. Use soapstone on areas you don't want solder or flux(if needed) to have contact with.

    Too much heat & all the solder leaks out, not enough heat and the solder does not flow.... Good luck!

    BTW - Acid base flux eats bluing, but....the heat from soldering has not affected the bluing on the guns I have soldered/sweated sights on and yes, regular lead tin solder is all you need.

    Pahtu.
    That's a great idea, actually. I hadn't considered trying to re-use the solder that's already there.

    We'll see what happens with the seller

  13. #12

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    Quote Originally Posted by Pukka Bundook View Post
    If you do solder it, a bit of non-corrosive flux will help, and also, don't play the heat directly on the sight, you need to warm the barrel and sight or the solder won't key right. I'd put barreled action in a padded vise, sight uppermost, tinned if needs be, then place sight exactly where you want it and run a wire over the sight, with a heavy weight suspended on it, so as the solder melts, the weight will cause the sight so settle down on to the barrel. as soon as sight is properly settled, remove heat.

    Good luck.
    R.
    Any suggestions for ensuring that the sight is properly aligned?

    I see that there's a screw at the back of the sight base under the leaf; I wonder if someone tried to overtighten it, breaking the solder free.

  14. #13
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    agree on the soft solder. PS.. you can get some pretty low temp high tin content ( flows good ) solder. As the others said, the 2 parts should be tinned.
    Sent from my Nokia 1020 win 8.1 phone

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    According to SA regulation from 1971 the original solder is tin/lead 50/50 alloy. Modern ones don't have lead probably but they contain flux, don't they?

    My experience in soldering is rather limited and as to Spitz sight jobs I've only corrected one B barrel front sight that was so badly crooked that windage adjustment wasn't sufficient to fix this. First I removed all the cosmo around the sight and removed the locking screw. I also used a long (and straight!!) aluminum profile whose opposite ends were standing on the ears of both the front and rear sight base. Then I heated the front portion (about 20cm or so) of the barrel just enough to melt the solder and when this happened, the front sight base became "slippery" and minor compression from above via the aluminium profile was enough to rotate the ears to correct position. No extra solder was added. In my case the problem wasn't loose joint of course. Just thought to add.

    I wonder if "professionals" did the rear sight without removing the stock as well.

    Last edited by CH; 04-19-2017 at 02:38 PM.

  16. #15

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    That's a very cool photo--thanks for adding that!

    I wonder if it was standard procedure to use another rifle as a brace for the one you're working on (looks like maybe an M27 ?)

  17. #16
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    Years ago when I worked for Du Pont we made Tetra Ethyl Lead additive for gasoline at my site. There was also still a lead pipe gang on the plant and I set a rear site on and M39 using the lead burners shop equipment with help from one of them. They had sheet lead in thin sheets like you see on most M39's holding the rear sight. we opened the circular sight bracket and heated the barrel then the sight bracket till is was right and slid the sheet lead in place till is oozed out on the table and wiped the joint clean of excess and allowed it to cool. we had lined it up cold with a device we called a miracle point and made witness marks to line it up when it was hot. When we got done it looked like many other M39's I had and is still in the safe among my other 48 I currently have. I do not recall using any flux but that is a lot of years ago so I can't be sure. Bill
    zeebill live from the hills of West Virginia!

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    I was thinking Acraglas.

  19. #18
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    Holds barrel liners in.... But... I like solder, braze etc
    Sent from my Nokia 1020 win 8.1 phone

  20. #19

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    The seller ended up giving a partial refund to account for the sight; so it looks like I'll be trying to sort it out one way or another.

    Anybody in the Louisville area (or general region) that would be interested in giving me a hand with this? I don't have the tools or experience to do it well, and the gunsmith's comments leave me feeling less confident in his ability to do a job that will satisfy me.

    It goes without saying I'll be happy to pay for the time

    Alternately, is there a shop anyone might recommend sending it to for this kind of work?

  21. #20
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    Quote Originally Posted by Rivaltm View Post
    Any suggestions for ensuring that the sight is properly aligned?

    I see that there's a screw at the back of the sight base under the leaf; I wonder if someone tried to overtighten it, breaking the solder free.
    The screw is only there to keep the sight indexed while you solder. The base itself is only a few thou larger than the barrel journals, so provided the set screw is in its divot and the base is seated to the barrel shoulder, it should self-align well enough. If it's out slightly for windage, all M39's have an adjustable front sight, but my guess is it will not be misaligned to any real degree.

  22. #21
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    Quote Originally Posted by CH View Post
    According to SA regulation from 1971 the original solder is tin/lead 50/50 alloy. Modern ones don't have lead probably but they contain flux, don't they?

    My experience in soldering is rather limited and as to Spitz sight jobs I've only corrected one B barrel front sight that was so badly crooked that windage adjustment wasn't sufficient to fix this. First I removed all the cosmo around the sight and removed the locking screw. I also used a long (and straight!!) aluminum profile whose opposite ends were standing on the ears of both the front and rear sight base. Then I heated the front portion (about 20cm or so) of the barrel just enough to melt the solder and when this happened, the front sight base became "slippery" and minor compression from above via the aluminium profile was enough to rotate the ears to correct position. No extra solder was added. In my case the problem wasn't loose joint of course. Just thought to add.

    I wonder if "professionals" did the rear sight without removing the stock as well.

    Any decent electronics store will still sell 50/50 pb/sn solder. It's only for water plumbing where it's no longer is use here n North America.

    I use PB/SN all the time for working on guitar amplifiers. Best stuff out there.

  23. #22
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    Lotsa auto stores now selling 95/5 tin/antimony.

    Amazon has it though.

    Electronics stores? Havn't seen a decent one in nearly 30ys!
    Sent from my Nokia 1020 win 8.1 phone

  24. #23

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    Click image for larger version. 

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ID:	2158866Anybody know what this marking on top of the receiver might mean? It's a Tula 1909 receiver if that narrows it down any.

    I just bought another B-Barrel off another board, so I may end up selling this one to someone with the tools and knowledge to fix it. Externally it's unissued; frosty but sharp bore.

  25. #24

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    I'm wondering if it's not a faint Liege Bomb proof. There's a second serial number (or some kind of ID number) below the Finnish serial.






    Click image for larger version. 

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    The reason I suggested epoxy is that heat often destroys bluing. Then you are stuck with cold blue, which is no more authentic than epoxy and is permanently disfiguring.

    You can't heat just the sight for solder to stick, the barrel also has to get very hot and you must apply an acid flux which also destroys bluing big time.

    Unless I am misreading the problem (always possible!) the sight is just wobbly. A little metallic filled epoxy like JBWeld under the sight might invisibly and reversibly stop the looseness with no possible bluing damage.

    I have taken apart soldered-on scope mounts from vintage PEMs and such rare scopes with a small torch as well as doing a lot of soldering, brazing and many forms of welding both stick and wire large and small when I was a welder - heat often changes surface finishes.

    Maybe soldering will leave the sight and barrel finish as-is, but I wouldn't bet on it. "First do no harm" works for rifles as well as sick folks.

    (Check out the guy in front of the torch flame in the above picture -he is already missing half his hair, fortunately on the side facing the heat! Maybe he is just warming himself up.)

    Quote Originally Posted by chasdev View Post
    Epoxy? Why not take it to a gunsmith and pay a few dollars and have it properly repaired/restored?
    Either that or send it back and get another, few as they may be, they are still around and in some numbers yet..
    Last edited by Stalin's Ghost; 04-20-2017 at 12:43 AM.

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    Sometimes simple works. Ask the russians how the felt being on on the other side of these technicians work ---opps that right you can't.
    "If it killed em 150 years ago it'll still kill em today !" Response to a question about black powder weapons

  28. #27

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    After tightening the locating screw, all of the play disappeared. I wonder if Locktiting that screw would work for non-combat purposes. It actually does seem that some combination of locktite and a strong adhesive ought to do the job

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    Is there some reason that the sight base itself can't be re-tinned and then drifted back into place? Then the barrel wouldn't need to be heated at all...

  30. #29
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    Quote Originally Posted by Stalin's Ghost View Post
    The reason I suggested epoxy is that heat often destroys bluing. Then you are stuck with cold blue, which is no more authentic than epoxy and is permanently disfiguring.

    You can't heat just the sight for solder to stick, the barrel also has to get very hot and you must apply an acid flux which also destroys bluing big time.

    Unless I am misreading the problem (always possible!) the sight is just wobbly. A little metallic filled epoxy like JBWeld under the sight might invisibly and reversibly stop the looseness with no possible bluing damage.

    I have taken apart soldered-on scope mounts from vintage PEMs and such rare scopes with a small torch as well as doing a lot of soldering, brazing and many forms of welding both stick and wire large and small when I was a welder - heat often changes surface finishes.

    Maybe soldering will leave the sight and barrel finish as-is, but I wouldn't bet on it. "First do no harm" works for rifles as well as sick folks.

    (Check out the guy in front of the torch flame in the above picture -he is already missing half his hair, fortunately on the side facing the heat! Maybe he is just warming himself up.)
    I've never seen soft solder heat affect bluing. Silver solder, yes, but not soft. He also may not need flux and the surfaces are already tinned.

  31. #30
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    High tin solder melts under 500'
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