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BT-99 Mainspring Installation???

Discussion in 'Shooting Related Threads' started by Rem870TB, Mar 1, 2009.

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  1. Rem870TB

    Rem870TB Active Member

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    Does anyone have a good teqnique for installing the mainspring in a BT-99.

    This spring, which measures about 3.8", uncompressed, has to be compressed quite a bit before it is supported completely by the mainspring guide.

    This is pretty challenging to do while trying to cock the hammer. IMHO, this is much more difficult that replacing Citori mainsprings.
     
  2. gun fitter

    gun fitter TS Member

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    I shouldn't answer since there are some here who don't think my posts have anything to offer.

    The trick is in using a stiff rod installed through the tang hole to capture the spring so it will compress and not collapse.

    It is still quite a job and fixing the trigger plate in a vise will help.
    A second pair of hands will also help.

    I do this operation inside a zip lock bag so parts don't go flying in to another county .
    Joe
     
  3. rennerize

    rennerize Active Member

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    I have a special pair of "pliers" that I made for that very thing. Otherwise it is very hard, be sure to wear your eye protection.
    Don
     
  4. Rem870TB

    Rem870TB Active Member

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    Thanks for the answers, so far :)

    Gunfitter; "I shouldn't answer since there are some here who don't think my posts have anything to offer."

    Well that one did, intersting, I did consider the rod idea, I will take another look at that.

    I do have a very good, padded vice.

    Don know what you mean about the protective eyewear, I wear my bifocal safety glasses w/sideshields for these "adventures"; good point.

    Don, since the pliers jaws would swing through an arc as they move, how do you keep the spring from buckling to the side?

    Once this is back together with a new spring, this little "episode" will not be repeated.
     
  5. TOOLMAKER 251

    TOOLMAKER 251 Active Member

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    I also have a pair of pliers that will compress and hold the spring and guide to reinstall, but if you drill a 1/16 hole through the rear of the guide pin 11/16 back starting from the end of the guide you can compress the spring on the guide and install a paper clip as a slave pin. Install the assembly and remove the paper clip and your back in business. If I recall 3200 Rem. spring and guide have this feature.
     
  6. JerryP

    JerryP Active Member

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    Rem870TB, I could see this post coming. Did you find a trigger return spring?
    You need three hands or a tool to put the spring back in place. I put the trigger housing in a wood padded vise. I use a tool that is a small hollow metal tube on a handle. Gunfitter describes the same procedure that I use. I insert the metal tube through the tang hole and push it up against the mainspring guide. It is tricky to do because the mainspring is being compressed as the tube goes against the mainspring guide. Then guide the spring into place in the tang and pull out the tool. It's a bit of a challange.

    To avoid a repeat of this "episode" don't remove the trigger housing without making sure the gun is cocked. It gets easier to install the mainspring after a few episodes.
     
  7. JerryP

    JerryP Active Member

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    I like toolmaker's slave pin idea. Have you actually done this on a BT? A paper clip will hold up against the the weight of the spring?
     
  8. TOOLMAKER 251

    TOOLMAKER 251 Active Member

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    JerryP, I have drilled 3 99's for people, yes the large paper clip will hold it. You can also use the 1/16 drill that you put the hole in with. If you have a length of tubing, file a slot across the end of the center of the tubing so when you compress the spring over guide you have access to slipping the pin in the hole once the spring is compressed slightly below the hole. You must be at least 11/16 from the end when drilling the hole. All this helps if your using a drill press. Always wear your eye protection.
     
  9. BT-100dc

    BT-100dc Active Member

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    Make sure you wear safety glasses and do the work inside of a box in case the spring slips. Darrell
     
  10. Rem870TB

    Rem870TB Active Member

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    "Rem870TB, I could see this post coming. Did you find a trigger return spring?"

    I shot trap for 39 years but this is my first BT.

    The hammer was "down" (released on a snap cap) when I dissassembled it. In my ignorance, I thought there was something to restrain the hammer from going forward enough to release the spring; never assume things, by the time I knew the score, it was game over.

    This is the first thing I have done like this in 20 years, from my viewpoint, this usually happens to "other" people.

    As for the part, there aren't any on this side of the border. Due to U.S. laws regarding export of fireanrms parts, we are looking at 4 to 6 weeks, minimum, before it gets here.

    Your post on the other thread was the first positive report I obtained on the "the spring", Browning Canada hinted that it must have been an "after market modification" too, they just don't know there.

    I was wondering if you measured your trigger pull weight before and after your spring broke. Mine was 64 oz before, 28 oz after the break.
     
  11. Rem870TB

    Rem870TB Active Member

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    Thanks, thats interesting, I sent a PM.
     
  12. chiefjon

    chiefjon Active Member

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    I took a straight blade screwdriver and filed a V in the end of the blade. I could then compress the spring to the proper depth.

    JON
     
  13. motordoctor

    motordoctor Shoji Tabuchi in Branson

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    how about a couple of pictures of the tool. thanks
     
  14. Rem870TB

    Rem870TB Active Member

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    UPDATE:

    Gun Fitter, I came up with a variation on your idea and IMHO, it works very well.

    I had a buddy machine a 3" long piece of 5/32" drill rod with a tappered hole in the one end to take the the tappered end of the Mainspring Guide and pass through the hole in the upright part back end of "Tang Piece" (That's Browning's nominclature, I would call it a trigger plate) that the Mainspring Guide fits through. The tappered hole in effect fits over the Mainspring Guide securely and acts as an extension for it,

    The drill rod serves as a temporary guide for the unsupported section of the Mainspring durring the initial part of the installation, keeping it from buckeling, which was my main problem. Without this, the spring bends, it can be straightened but I don't trust a spring that has been bent, I have a new one on order, too.

    Once you get the hammer cocked and secured, the drill rod temporary guide easily drops out the back of the Tang Piece.

    I found this doesn't require a lot of effort to use and a spring can be installed in a matter of a minute or so.

    I am rather pleased with this simple design for a temporary installation tool.
     
  15. BB2506

    BB2506 TS Member

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    Here's a fairly easy way, clamp the pin with the spring on it in a vise.
    compressing the spring a little
    use a screw driver with a v notch in it to compress the spring a far as it will go use the jaws of the vise as a lever point for the screw driver
    with the spring held back, pinch the pin just above the compressed spring with
    a small pair of needle nosed vise grip pliers, useing the only the tip end of the pliers you can now take the clamped pin & spring and installed it in the reciever very easily
     
  16. JerryP

    JerryP Active Member

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    Rem870TB , Do you have the trigger return spring yet?
     
  17. Rem870TB

    Rem870TB Active Member

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    "Rem870TB , Do you have the trigger return spring yet?"

    Oh no, we can't expect miracles, can we? ;)

    Lets just say, I have gotten "creative" in getting one and hope to have it next week. Should have done that some time ago, live and learn.

    If the other source EVER comes through, I will keep it as a spare, since they seem hard to come by.

    At least when I get it, re-installing the mainspring will be a 2 minute job with that new tool I had made up, since I tested it on the old mainspring; no big deal to put in now.
     
  18. Rem870TB

    Rem870TB Active Member

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    Installing A BT-99 Mainspring; UPDATE

    I came up with a way that works for me with my own design of guide.

    The problem is, the mainspring is much longer than the mainspring guide and you are trying to compress the spring, initially with almost 1/2 of it unsupported. Not a nice job.

    This is harder to describe than it is to do.

    Safety eyewear is mandatory, if this goes bad, a person could lose an eye, as you likely know, these are strong little springs,

    I had a retired Engineer & Metallurgist buddy of mine take a 3" length of 5/32" drill rod and machine a tapered bore on one end to fit over the tapered end of the guns mainspring guide.

    The 5/32" rod will pass through the bore of the mainspring and the hole in the trigger group that the gun's mainspring guide passes through.

    I set the trigger group, carefully in a padded vice.

    I then pass my temporary guide through the hole in the rear of the trigger group where the mainspring seats.

    I place the mainspring over the temporary guide, then get all the other parts ready.

    The hole in the rear of the trigger group doesn't allow the temporary guide to line up in a straight line with the spring and the guide but it only requires a gentle curve so the spring isn't hurt.

    Line the main spring guide, associated parts and the spring in such a way that the main spring guide "plugs into" the tapered hole in the temporary guide.

    Once this is done, the spring is supported on it's entire length and can be compressed by hand and the hammer cocked.

    Concentration is a must but if I can do it easily, in one try, it can't be too bad.

    Once the hammer is cocked, the temporary guide comes out the back end of the trigger group and you are done. Carefully reinstall it in the receiver.
     
  19. erm

    erm Member

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    Rem870TB,
    Nice work explaining the procedure but what do you mean when you say "hammer is cocked" in the third line from the bottom? Do you mean that when the front of the mainspring guide slips into the depression behind the hammer or actually use the barrel to cock the hammer? Compressing the spring is easier said than done even with a tempo guide. Compressing the spring even with a tempo guide rod is my problem.
    Elton
     
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