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Need Bt-99 top lever screw and main spring advice.

Discussion in 'Shooting Related Threads' started by StansCustoms, Mar 3, 2012.

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  1. StansCustoms

    StansCustoms Well-Known Member

    Joined:
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    I'm replacing the springs in my BT-99 (circa 1982)..and doing some general maintenance and removing a release trigger. I have ordered a Field Manual...but it'll be a week probably before I get it. In the mean time maybe I can get the information I need in TSC..and get it back together sooner.

    So far I have two problems.

    Number one is that the screw in the Top Lever is tight, tight, tight...It can't ne left handed can it..?? Any comments on this at all?

    Number two.. Reinstalling the mainspring is tough...in fact I believe I may not be going about right. I have been working with it enough that I am intimately familar with it...if any one can decscribe the easiest way to reinstall it. I would sure apppreciate the input.

    Best regards..Stan
     
  2. Johnny

    Johnny Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    2,804
    Stan , the top lever screw is a standard screw, not left handed. My top lever broke and the screw was also very tight. Apparently tightened with an impact wrench. Forget about using just a screwdriver. I resorted to clamping the receiver in a machinist vise on a drill press. I put the proper size parallel screwdriver bit in the chuck. I lowered the bit into screw locked the two together. I put a wrench on the bit and smacked it with a hammer and popped it loose. A milling machine would be better. You may be able to use an impact wrench to loosen it but be very careful of stripping the screw head. Might want to go ahead and order a screw.

    You need a tool to change the mainspring, or a very big guy to help. If you bought a spring here from Jim Flynn it will be a little harder, his spring is stiffer than factory.
     
  3. StansCustoms

    StansCustoms Well-Known Member

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    Very much obliged Johnny...

    I'm a retired mechanic by trade..(i.e. Stan's Customs)and I "really" had some pressure on the screw with a quality screw driver...I knew that I was just on the verge of slipping out of the slot, which would bugger the slot and then I'd really have a problem. Plus it is at a slight angle.

    Evidently you had the receiver split to chuck it up for access on a mill or drill press. I have all the pins out of the receiver and still don't have the top separated from the bottom, as per parts diagrahms. Without a manual(which is on order)...I'm going very slowly...being careful not to damage the receiver.

    Does the receiver need to be separated (top from bottom)? If so is there any concealed pins that are easy to miss...or any particular approach to convincing it to separate.

    Regarding the tool for installing the mainspring...do you know a source for that. I Googled for one but came up with nada.

    Thanks for your assistance..
    Best regards..Stan
     
  4. Phillip's Gunsmithing

    Phillip's Gunsmithing Member

    Joined:
    Apr 13, 2008
    Messages:
    217
    Location:
    Texas
    If you call me I will walk you through taking your action apart and installing the spring.

    Phillip Crenwelge 210-313-5988
     
  5. Johnny

    Johnny Well-Known Member

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    Stan, You will need to remove the trigger assembly. You will have to do that to change the mainspring anyway. Remove the large pin in the receiver and use a hammer and wooden dowel to push the trigger housing out. The Field Manual will show how to do this. I damaged my screw head trying to use a screwdriver but using the drill press I popped the screw loose with no further damage. Be sure you lock the screwdriver bit to the screw in the drill press so it cannot slip. The bit will have wrench flats. Smack the wrench with a hammer and it will pop the screw loose. If you totally ruin the screw head you will be in trouble.

    ATTENTION, before you take the trigger housing loose, cock the trigger. Leave it cocked while you remove the housing. If you pull the trigger while the housing is removed, the mainspring will be launched into orbit. Hold it in your hand or cover it with a rag to pull the trigger.

    The tool you need to change the mainspring is something you will need to make.
    I used a 5/32 welding rod about 4-5 inches long. beat the coating off and drill an eighth in. hole in the end of the rod, parallel to the rod. I put a file handle on the other end. Clamp the trigger housing in a vise. Push the tool through the hole in the back end of the trigger housing. Put the hole in the tool up against the end of the mainspring guide to hold it in place while you compress the spring and slip it in place. It is tricky to do and may require some practice to figure it out.

    Also, If you change the mainspring, you may also have a top lever spring included. Just pry out the spring with a screwdriver. Place a rag over this or you will lose the little insert in the end of the spring. It will also be launched into orbit and you won't find it. The field manual will be a big help, it is full of info.
     
  6. Johnny

    Johnny Well-Known Member

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    Just saw Phil's offer, I would take him up on it.
     
  7. StansCustoms

    StansCustoms Well-Known Member

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    Johnny..

    Thanks for the information. I thought it might require a little help, but I have nothing to go on till I get the manual. Many thanks for the tip.

    That also clarifies the mainspring issue as well.

    I had already figured out the top lever spring removal...popped it out while I was holding the receiver in a 2 gallon plastic bag, which was another poster's suggestion. Helpful idea.

    BT-99's look to be about as simple as things come...once you determine the proper way to disassemble it. The idea is not to scar the darn thing up while you are learning...in other words, stop when it balks...and ask someone that knows, or wait till you get get a "good" manual. Seems like time is always of essence so I decided to try the internet while I'm waiting on a manual.

    I wish information had been as accessible when I was younger...it would have been a lot easier to learn my trade. I spent a fortune on a Service Manual's down thru the years. Many times they were incomplete and mechanics still had to work out the problems on their own....especially on "new" cars where service manuals wern't available till later in the model year. On top of that, we often had to deal with problems that the manufacturer didn't even know they had till after production. Those issues were really fun...and what generated recalls.

    Guess I'm showing my age...ain't the internet wonderful...LOL!

    I saw Phil's offer to another poster too...very nice of him. I just wouldn't want to have to depend on anyone else for this type of thing. So I'll spend the extra time to get thoroughly acquainted with the procedure. There always is the "first" time for everything. Some are just less painful than others...hopefully this is one of those. Heh heh!

    Thanks again and Best regards...Stan

    Woah...I didn't see Phil's post to me, I was talking about the one where he offered to remove the release free to some one else...for the release, on another thread. I was pecking out my post when he offered to help me. Thanks Phil, I will call .
     
  8. pulllit

    pulllit Member

    Joined:
    Jan 29, 1998
    Messages:
    231
    Location:
    Southern part of IL
    I have found that a valve spring compresser made for a lawnmower engine works best for installing the mainspring. KD Hand Tools number 379 Small Engine Valve Spring Compressor. The tool jaw can be adjusted to fit the mainspring sleeve keeping it contained while the spring is compressed.

    NAPA, Advance Auto, Sears would be a good source. Around $30.

    _
    [​IMG]
     
  9. moman3

    moman3 Active Member

    Joined:
    Aug 23, 2010
    Messages:
    104
    Location:
    Covington Washington (South Seattle area)
    To re-install (and remove for that matter) the mainspring, I found that you really do need to split the receiver. Take the vertical set-screw out holding the cross pin, drive the pin out, and split the receiver case inside of a kitchen bag, or while holding rags over it to catch the mainspring guide pin that's about to dislodge.

    Then clamp the trigger group in a vice as shown below. The only "tool" you need is a bit of brass tubing, - I used brass tubing found at a hobby store, or a "good" hardware store. I happen to have some used for R/C model airplane glow fuel line piping.

    Swedge the tubing over the pointed tip of the main spring guide pin:

    Slide the brass tubing fitted guide pin thru it's hole.

    With your thumb and forefinger, put the ball of the guide pin in the recessed hole in the hammer, and simply push back on the hammer with your thumb while holding slight pressure on the end of the brass tubing on your left hand. If you swedge the tubing on hard enough, you won't even have to hold/guide the spring with your left hand.

    Depressing the spring isn't really that hard since the hammer itself acts as a lever in a way.

    When the hammer latches, simply pull off the brass tubing:

    Re-install the trigger group withOUT pulling the trigger!

    As far as the screw, "screw it", - I'm battling that right now. I can't get it out, and tried every technique mentioned here (and elsewhere). It just ain't happening, period. And now, the edges of the slot are rounded off enough now that if I really wanted it out, I'd have to drill it out.

    Bottom line, there is no practical reason that I could think of for having to remove that screw anyway, unless for personal challenge. You can do ample cleaning with it, and the top lever and slide bar in place. Just "clean around it".

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


    UPDATE:
    I did hand up getting the top lever screw out!

    I handed up buying a nice DeWalt 1/4-inch impact driver. It took some doing (bit slipping off at first), but after some finessing, and I DO mean finessing the trigger to get a nice, light, tick-tick-tick impacting action, it came loose. I'm so happy :)

    And you can see the brown ick on the threads which I presume is rust. The new screw is going to get a nice light coat of Anti seize, that's for sure!

    [​IMG]

    [​IMG]
     
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