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Thread: C 308/Cetme C - cocking handle not fully unlocking rollers

  1. #21
    Senior Veteran jkv45's Avatar
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    Quote Originally Posted by scooterwrench View Post
    The washer idea may not be a good choice. The problem I see is the hole in the washer. Your cocking handle will start to unlock the bolt then drop off into that hole making the spacer useless.
    I need to look closer, but I was thinking about placing the washer inside the cocking handle carrier, where the bolt carrier contacts - and not at the end where the handle cams.

    If it was at the end, then yes, it would drop into the opening in the washer as the handle was rotated. In that case, I would use some type of hardened shim, possibly from a motorcycle engine with "shim under bucket" valve adjustment.

    Is there any disadvantage to running it towards the minimum end of the bolt gap tolerance?

  2. #22
    holescreek's Avatar
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    Is there any disadvantage to running it towards the minimum end of the bolt gap tolerance?
    Nope, it just takes it a little longer to unlock. Nothing noticeable to the shooter.

  3. #23
    Senior Veteran jkv45's Avatar
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    Quote Originally Posted by holescreek View Post
    The universal "sweet spot" for gap is said to be .016". I don't exactly know why it was chosen, it was decided long before I got into the Cetme game. Any gap between .004 and .020" is within spec.
    If you switch to a NOS bolt head your gap will likely increase a little bit due to not having any wear in the front roller window.

    Original bolt head length is 1.823" Every ground bolt head I've held or heard of has been 1.812". If you measure a .025" gap it's really a .014" for calculation purposes.
    I just checked again, and it looks like the specs I found for an original bolt head weren't correct. I had been using 1.834/5" as the length - and not 1.823".

    My bolt head measures 1.822" - so it's not been ground apparently.

    Measuring in a normal manner, I now get .016" bolt gap - so I'm good.

    Still working on a solution for the cocking handle issue.

    Thanks.

  4. #24
    Senior Veteran jkv45's Avatar
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    As far as a solution to shimming the excess cocking handle carrier gap, the inside dia of the cocking handle carrier measures 15.5mm.

    The outside dia of the bolt carrier that rides inside it measures 14mm.

    I checked with a couple of the motorcycle shops I frequent, and there aren't any valvetrain shims in that size.

    Need to start looking for hardened washers. The thickness is going to be in the .030" to .035" to get the proper gap.

  5. #25
    holescreek's Avatar
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    The inside diameter of the cocking tube is .707" IIRC.

  6. #26
    Senior Veteran scooterwrench's Avatar
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    Mcmaster-Carr sells shim stock in a wide variety of thicknesses. Comes in SS,spring steel and plastic. I would use the spring steel if I were doing it. A good place to shim would be the inside of the cocking handle support where it contacts the carrier tube. You could grind a disc that would be a press fit or use some kind of silly epoxy to hold it in place.
    Gun control is the ability to hit the target.

  7. #27
    Senior Veteran jkv45's Avatar
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    Quote Originally Posted by scooterwrench View Post
    Mcmaster-Carr sells shim stock in a wide variety of thicknesses. Comes in SS,spring steel and plastic. I would use the spring steel if I were doing it. A good place to shim would be the inside of the cocking handle support where it contacts the carrier tube. You could grind a disc that would be a press fit or use some kind of silly epoxy to hold it in place.
    That seems like a good place to add the shim/washer.

    I used a .040" washer inside the cocking handle carrier to test it, and it seemed to work, but I need a washer closer to .025".

    I've been checking McMaster-Carr, and may need to buy a bag from them if I can't find a single washer, but I need to know exaclty what thickness is required first.

  8. #28
    Senior Veteran scooterwrench's Avatar
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    Did you have any free play with the .040" washer? To check free play allow the bolt to slam home then drop the hammer against it. Pull out on the cocking lever just enough for it to clear the lock pin and see if you can move the cocking lever cylinder fore and aft. I feel a minimum would be about .010" and a max at .030"
    Gun control is the ability to hit the target.

  9. #29
    Senior Veteran jkv45's Avatar
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    Quote Originally Posted by scooterwrench View Post
    Did you have any free play with the .040" washer? To check free play allow the bolt to slam home then drop the hammer against it. Pull out on the cocking lever just enough for it to clear the lock pin and see if you can move the cocking lever cylinder fore and aft. I feel a minimum would be about .010" and a max at .030"
    No. There was no play at all. You could see it moving the bolt carrier when you moved the handle, and I measuered an increase in the bolt gap - so too much.

    I reassembed it and checked the gap again without any washer, and it isn't as much as I had previuosly thought. Looks more like .030" now, which doesn't leave me any room to change it.

    It's still pretty difficult to open it up, but I'm going to shoot it a bit and see what it does.

    Thanks again guys.

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