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Thread: modify military trigger with ball bearing

  1. #1
    Boolit Master
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    modify military trigger with ball bearing

    Yup I did it. Got to looking at those hump thingies on my carcano trigger(it really is not bad after cleaning and light polishing) but I wondered how a ball bearing set into the hump would work. To the mill and some crazy glue and have a bearing set into middle hump making it look like it grey into the metal! Figured I would use the middle hump and keep it higher so the rear hump isn't needed. It works real good. Has a first stage that comes back a little(real easy like and then it hits a wall and you apply your finger to fire) and it has about a 5 pound pull but it breaks like glass, so the heavier pull than desired is quickly forgotten. Now I got the idea to find a thin piece of stainless steel and fit and glue a thin piece into reciever for ball to slide on. Should be better yet I believe. Any body else ever try this? The sear and cocking piece were nasty looking so I filled them with diamond files to a nice clean surface. The sear sets about as high unto cocking piece as the original piece. I included that info for the naysayers who might think I got the sear too shallow on cocking piece.
    Look twice, shoot once.

  2. #2
    Boolit Master
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    I have been making a Roller Ball bearing trigger for for the Mausers for years .
    And modifying them to make them Adjustable.
    I have made other adjustable triggers for the other military rifles also, and i think the Carcano was one of them.
    I isnt that hard, and can be done at home with simple tools like files and a Mapp Gas torch to braze parts on the the original triggers.
    The gluing a Piece od Stainless steel to the bottom of the receiver to give a harder smoother surface does work, but I used a piece of an old Tape Measure.
    Works good because it is tempered and already curved to better fit the receiver.
    Last edited by LAGS; 08-26-2017 at 09:31 AM.

  3. #3
    Boolit Bub
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    How 'bout some pics?

  4. #4
    Boolit Master
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    I am having trouble posting pic's right now.
    it says I have too many pictures uploaded and have no more space to download more.
    I someone could tell me how to delete the old pic's , then I could post some new ones.
    Or PM me an Email Address and I can send them to you.

    If these pictures come thru, they are the only ones I already had downloaded to the Manage Attachments File so far.
    But I have more on my computer that it wont let me download to the site
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by LAGS; 08-27-2017 at 10:21 AM.

  5. #5
    Boolit Master
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    Well , It did work this time.
    This is a standard Mauser 98 trigger that I welded a small piece of metal to the front of the trigger then drilled and tapped it for a 6/32 set screw and installed a jamb nut.
    This is the trigger pull adjustment.
    The other adjustment is on the front at the trigger return spring part of the sear body.
    I drilled and tapped the sear body and installed a set screw to be the Overtravel stop.
    Both of these modifications work great by themselves even without adding the Roller Ball.
    The 1/4" roller ball is installed by cutting a notch in the rear part of the trigger where the double humps on the trigger were.
    But dont cut too deep or the ball will not be high enough to hit the bottom of the receiver properly.
    You have to file two small groves inside of the Sear Body to make room for the ball to fit inside and act as a guide for the ball to slide in.
    Now rather than welding a piece of metal to the trigger, You can Silver Solder or Braze a 6/32 Nut to the front of the trigger for the pull adjustment set screw.
    And depending on the length of what is installed on the front tab of the trigger, you may have to file a small bevel to the Magazine Box at the housing for the Magazine latch plunger housing.
    I hope this helps.
    And if I remember correctly, the Carcano has a similar trigger set up, and might be able to be modified in the same way with the loose roller ball set up.

  6. #6
    Boolit Bub 405grain's Avatar
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    I made Mauser ball triggers using LAGS information for a couple of small rings, and they work great! What a huge improvement over the military trigger. The modification wasn't very hard to do, and it was a fun project. One thing that I did which he didn't mention was to replace the factory trigger group pins with 3mm dowel pins. This gave an even smoother trigger pull. The target groups really shrank after I did this modification. I would recommend it.

  7. #7
    Boolit Master
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    @ 405grain.
    Yes you are correct about the trigger pins.
    And on some rifles I put in shim washers made out of brass or Feeler Gages to center the trigger better and eliminate any side to side wobble

  8. #8
    Boolit Bub
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    The information you have posted is very appreciated. I can't wait to get to this on many of my triggers. I have done the trigger pull adjustment for quite a while, but will add the Overtravel stop and Roller Ball mods with new pins now, to see how that effects the pull. I have a Huber Trigger on one of my rifles, which seems to be very similar, and it works very well.
    I am curious that the roller ball does not move on the trigger, but is brazed in place. Can't wait to try it. Thanks
    re

  9. #9
    Boolit Master
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    On the triggers that I do the ball is floating on the Sear housing and the ball actually rolls a tiny bit.
    If you have a ball brazed in place to the trigger , it just works as a Smooth hard dome to pivot on

  10. #10
    Boolit Bub
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    Lags,
    How do you get the ball to float on the sear housing? I am not sure I quite understand what you are doing differently. Please explain it in a little more detail for us dense and disturbed...
    Thanks
    re

  11. #11
    Boolit Bub
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    LAGS,
    I just reread your post on how to do this, and I have a couple questions.
    Are the two grooves cut vertically on the insides of the notch you cut in the sear?
    When you say don't cut the notch in the sear too deep, do you mean you are cutting from the bottom and wish to keep it from going through the top of the sear? Or are you cutting the notch from the top and setting the ball down in it?
    I am still a little confused, and I really want to get this right...
    re

  12. #12
    Boolit Master
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    The Ball bearing is 1/4" diameter.
    The inside of the sear housing is just a tiny bit less.
    So I take a chainsaw file and file two groves in the inside of the sear Housing body ( one on each side )to allow the ball bearing to fit into as seen in the picture shown from the top, ( I think the third picture )
    The TRIGGER is the part where you dont want to cut the notch for the ball too deep.
    You want the ball to sit in the trigger notch, and stick up out of the sear housing about the same height as the Hump would have been on the trigger before you notched the trigger.

    If you look closely at the first picture,
    If you look at the Sear ,(that is on the left) you can see the slight concave line or groove filed in to the inside portion of the slot where the trigger and ball will fit into.
    It makes it like a guide for the ball to slide up and down in.

    A note.
    If you get to agressive on filing with the round file or chainsaw file, and the ball rattles from side to side in the sear housing too much.
    You can then get you a 5/16" ball bearing to replace the 1/4" ball bearing
    Last edited by LAGS; 08-28-2017 at 11:31 PM.

  13. #13
    Boolit Master
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    If I had the ability to post pictures better, I would do a step by step tutorial on how this is done.
    But I saw this same thing shown in Gunsmith Kinks 2 on page 358 many years after I had been building them for my rifles.
    Not saying I invented this design, but it has been around for a very long time same as the adjustable set screws that I combined with the roller ball trigger.
    It isnt a Timney trigger, but it is a WHOLE LOT better than the Military trigger.

  14. #14
    Boolit Bub
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    Thank you so much LAGS. Very helpful. Off to the bench to perform surgery now...
    re

  15. #15
    Boolit Master
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    @ Red Elk
    You are welcome.
    I am glad to help others where I can.
    But the suggestion about going to a lighter trigger return spring is valid.
    As you can tell in the third picture.
    The spring is shiny.
    That is because it was replaced with one I bought at a local hardware store.
    I cut it to a tick longer than the factory spring.
    But make sure it is strong enough to positively return the trigger each time the bolt is cycled.
    Otherwise on a fine adjust trigger , it will not raise the Sear high enough to positively catch the cocking piece on the bolt.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check