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Old August 28, 2012, 03:25 PM   #1
calinb
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Join Date: October 18, 2008
Posts: 10
Win M70 MOA Trigger Jamming

I hope someone here can give me some tips on what appears to be a trigger problem. I have a new Ultimate Shadow M70 in 338 Win Mag. Never fired (other than dry firing). I got it NIB off a GB auction. I dry fired it a few times upon arrival and immediately put a new lighter trigger spring in it from Ernie and adjusted the MOA's set screws to around 3 lbs. pull and minimum over-travel necessary to get trigger release. The trigger passed the "whack the buttstock hard on the floor" test.

I don't know if it had this problem before I made the changes but every dozen or so pulls of the trigger, the trigger jams after cycling the bolt for the next pull when dry firing. I tried backing out the set screw to increasing the over-travel significantly but no improvement in trigger reliability.

Upon removing the trigger housing after each failure, The actuator appears to be jammed in the "trigger released/pulled" and it is holding the trigger firmly in the trigger back position. When I attempt to move the actuator with a small pin punch, I can move it back and forth, but I can feel that it is binding on something. When I punch out the roll pin to remove it, it comes out fine and I can't find anything wrong (marks on it, etc.) It installs back into the housing perfectly and functions normally upon reassembly--for several more pulls of the trigger until it jams again.

I removed all the trigger components from the trigger housing last time but see no signs of the origins of the jam. Maybe someone else has had experience with these symptoms. Maybe I should polish all the surfaces, coat with layout blue, and reassemble.

Thanks for any advice, experiences, or tips!

-Cal

Last edited by calinb; August 28, 2012 at 03:50 PM.
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Old August 28, 2012, 03:45 PM   #2
hooligan1
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You should only clean your new trigger with "white gas" (coleman fuel) and then lubricate it with lighter fluid, (i use ronson) for some reason any kind of heavier lube makes triggers act funny.
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Old August 28, 2012, 03:48 PM   #3
calinb
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Join Date: October 18, 2008
Posts: 10
Thanks! That's worth a try. I used KG5 trigger lube, which is super light.
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Old August 28, 2012, 07:40 PM   #4
calinb
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Join Date: October 18, 2008
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Hopefully, I fixed it. I noticed that the edges of some of the access holes in the trigger casting weren't perfect. The flaws were very subtle but, with a hand lens, I could see some small areas around the perimeter of the holes with flashing that was left behind after the countersink de-burring operations on the interior surfaces. The actuator slides past these holes, though it is narrower than the internal dimension of the housing by a fair margin (it's only full width near the pivot pin).

Regardless, I decided to clean-up and polish the interior walls of the housing. I used a file, cratex bit, and a patch on a popsicle stick with Flitz polish to clean up the inside of the housing--especially around the holes. After a thorough cleaning with TCE spray cleaner, I re-lubed with KG5 and put it back together. Time will tell but I dry fired it a number of times without the trigger lockup.

Thanks for the help, hoolligan1. Your advice got me thinking that triggers can be very sensitive to contamination, lubricant, and, similarly, small imperfections in the finish--even apart from the sear surfaces, which I didn't touch by the way. The trigger already has an excellent quality so I decided to not "fix" that!

Last edited by calinb; August 28, 2012 at 07:46 PM.
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