Swiss k31 cocking piece sear dimesnion

[Lucite]

I was wondering If anyone with an unmodified k31 cocking piece would be able to tell me the dimension of the sear on the bolt cocking piece measured from the points in the picture below. I have a feeling mine has been modified because there seems to be signs of metal being removed in addition there's no second stage to speak of. Also the measurement I got was .683" if anyone is interested.

 

[TheArmyMan204]

Mine is .0688" at the highest point. .005" difference is well within tolerance I think your fine friend

 

[Lucite]

Thanks for they reply, I believe I found the problem elsewhere in the trigger mechanism. upon further inspection I found that the pin that the first stage rotates on ("C" in the image) looks like it has been filed down in order to remove the second stage. Now I think the only course of action would be to file down notch "B" or drill out the pin and replace it with one of the proper diameter.

Filed down pin

 

[diopter]

Have a look for posts by parashooter.
http://theswissriflesdotcommessageb...e=0&beforeafter=after&orderby=relevance&boxes[]=5&boxes[]=10&boxes[]=15&submit=search&advanced=1

I suggest wrapping some alum window tape around the pin to confirm your theory.

 

[Lucite]

I never thought of using aluminum tape, I do however have an assortment of steel shim stock. I'm also pretty sure the pin has been modified, to be sure I would need the od of one on a rifle with an un modified trigger group and to eliminate any other doubts I would also need the oal of the trigger bar to be sure that the sear surface hasn't been changed as well.

 

[diopter]

I'll try to measure one, whenever I get home.

 

[diopter]

Pin OD 0.1160" - 0.1170"
Can't measure the spots with the most wear.

 

[Lucite]

With out a O.D blade mic there's no way for me to get an accurate measurement to see how much has been taken off, and I'm coming up with a similar measurement to what yours is. As for the "trigger bar" I got a measurement of .265 measured from the points shown but it doesn't seem to have metal removed so I'm thinking the pin is the culprit, and thanks for the help its greatly appreciated.

 

[Lucite]

well this is interesting, playing around with the trigger some more it looks as if the pin was filed down to bring it closer to the second stage rather than go in the opposite direction, and after reading through the armourers manual it seems whoever did it had the right idea but wrong method.

 

[diopter]

That one of mine also in the 0.265" range.
You have any friends who also have a k31 you can exchange bolts with to see if the problem persists?
I'm thinking weak firing pin spring.

http://theswissriflesdotcommessageboard.yuku.com/topic/9022/Its-Here?page=1
Guisan's posts #8 & 10

 

[diopter]

Let's back track a bit.
Some metal wear is normal.

1st stage is all takeup until slight resistance from sear .
2nd stage is crisp sear release from there.
Suggest comparing it with other k31s.

 

[Lucite]

The firing pin drops before trigger point D makes contact with receiver point E and if I had to guess the point at which it releases there's about a .020-.025 gap between D and E

Edit
After spending and hour or two with a diamond needle file, some machinists blue, and 2000 grit sandpaper I have achieved the 2 stage trigger. What I ended up doing was filing notch B with the diamond file until I got it close to what I wanted then using the machinists blue I trued the notch up as best I could again with the file. Once that was done I used the machinists blue to find any high spots in the notch and proceeded to polish it with the 2000 grit sand paper. I also polished pin C and the sear surfaces of the trigger bar and cocking piece and while its not match grade I would feel comfortable calling it in the very least service grade and now its not nearly as light as it was when I first got it.