Gunsmithing M700 squirming bolt

Stringer

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Dec 27, 2008
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When I dryfire my 700 on an empty chamber, the bolt moves forward about 0.020". It seems like the sear and firing pin mechanism pull the bolt rearward. The large 0.020 (measured with feeler gauges) concerns me.

When I put a dummy round in the chamber and dryfire, the bolt twists slightly counterclockwise, but doesn't move longitudinally like it does on an empty chamber.

Is my timing off? Whats the deal?
 

Hateca

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  • Aug 12, 2004
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    Re: M700 squirming bolt

    No not necessarily and most likely not. You just have a sloppy factory bolt / raceway and sloppy cocking piece grove fit in the receiver. Normal for factory Remington.

    What you are seeing is the relationship between the bolt cocking piece and the sear. When you dry fire on an empty chamber the movement of the firing pin forward hitting nothing but the firing pin stop inside the bolt body will cause the entire bolt to want to keep moving forward. (Object in motion stays in motion until acted upon) There is no cartridge in the chamber taking up the headspace to stop it. The bolt handle will sometimes also jump.

    With brass in the chamber, empty or live, and you dry fire releasing the firing pin the firing pin assembly wants to now center, but the bolt won't move forward now because the round is in the chamber (Headspace).

    The reason is when you cock the bolt the firing pin assembly wants to over rotate to the right because of slop in the works, the sear will now hold it there until you pull the trigger. Now when you pull the trigger, and with nothing to hold the cocking piece and the pin assembly to the right, it will want to rotate back to the left when you pull the trigger releasing it.

    On some custom action the tolerances are tightened up to eliminated a lot of what you are seeing. There will be tighter tolerances in the bolt and raceway fitting. The grove for the cocking piece will be tighter to keep the firing pin assemble from over rotating and a bunch of other things.

    For factory receivers bolt sleaving was something done to help, oversize cocking pieces so they could be fitted to the grove cut into the receiver and so on.

    You have to find a happy medium with a field rifle or tighter tolerance will cause you other problems. Factory rifles are in most cases on the loose side so they will work in all kinds of conditions.

    If something concerns you have a competent person look at it and have the headspace checked. It just sounds like you have a typical factory Remington rifle.
     

    jimurphy

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    Jul 30, 2009
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    Re: M700 squirming bolt

    There is nothing really wrong, you simply have greater space between the bolt face and the face of the barrel. Usually .005"/.010" , yours is .020", with a case in the chamber the bolt is held to normal headspace. Sloppy, but safe.
     

    Stringer

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    Dec 27, 2008
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    Re: M700 squirming bolt

    So long as it's safe. I assume that one day when I may rebarrel this action, this distance can be reduced?
     

    Hateca

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  • Aug 12, 2004
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    Henderson NV
    Re: M700 squirming bolt

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Stringer</div><div class="ubbcode-body">So long as it's safe. I assume that one day when I may rebarrel this action, this distance can be reduced? </div></div>

    Yes