Gunsmithing FN SPR Bolt issue

rossneder

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My SPR seems to stick in the last few degrees of bolt lift. In other words just as the lugs are lining up to clear there is a bit of resistance. It is most noticeable after a round is fired, sometimes requiring quite a slap to finally open the bolt.

I assumed it was the cams, but they are perfect. I also looked carefully at the lugs and they make full contact equally on both sides.

I'd bet somebody has struggled with this, any directions?

Thanks,
Ross
 

LR-WSM

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Re: FN SPR Bolt issue

Just a guess but have you looked at the top and bottom front edge of the claw extractor. A fired piece of brass might be pushing it out far enought that it's making contact in with the groove that was cut to clear it. Use a sharpie on the top and bottom edge as well as the back side of the nose. Then get a fired case, preferably one that was tight on extraction and cycle it. The groove might be a little shallow or you might be running the pressures a little high.
 

rossneder

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Re: FN SPR Bolt issue

It has good clearance there, beside it has the resistance even with the extractor removed. I'll bet this is something really simple and I just can't find it.
 

LR-WSM

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Re: FN SPR Bolt issue

Check the connection point where the bolt handle is solderd to the bolt body. It is timed to ride the extraction cam ramp ( made that name up, I know just enough to get in trouble ) Possible your handle might be set a little to close. As before, check this with a case in the chamber.

In case it's not that, does it feel like it's binding or rubbing at the front or the rear of the bolt? Might have a bound up spring thats screwing with the cocking piece.
 

dmg308

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Re: FN SPR Bolt issue

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LR-WSM</div><div class="ubbcode-body">Check the connection point where the bolt handle is solderd to the bolt body. It is timed to ride the extraction cam ramp ( made that name up, I know just enough to get in trouble ) Possible your handle might be set a little to close. As before, check this with a case in the chamber.

In case it's not that, does it feel like it's binding or rubbing at the front or the rear of the bolt? Might have a bound up spring thats screwing with the cocking piece. </div></div>

Negative FNs are not the same as remingtons no soldered on bolt handles.Are you using reloads?
 

rossneder

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Re: FN SPR Bolt issue

Yes to the reloads, but a mild load.

Maybe the timing is off. The case is fully extracted when the last few degrees of rotation get resistant.

Next time you are by your rifle cycle the bolt and see if there is a noticeable change in torque for the last few degrees. On mine it is there with or without a case, but worse after a round is fired.
 

sickeness

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Re: FN SPR Bolt issue

I had the same problems but with hot 175gr reloads. No problems like this with factory 150 and 168gr ammo.

What bullet were you shooting?
 

Hateca

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    Re: FN SPR Bolt issue

    Check and see if the second from the front scope base screw is a little too long and is sticking into the receiver.
     

    PLeighton

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    Re: FN SPR Bolt issue

    Does it do it with the safety engaged in the middle position?
    If it doesn't, then the issue is with the cocking mechanism.

    With the bolt closed, move the three position safety to the middle position.
    Open the bolt and then remove it from the action.
    Depress the "Breech Bolt Sleeve Lock" with your finger and unscrew the "Breech Bolt Sleeve".

    Examine the firing pin assembly aka. "Breech Bolt Sleeve".
    Clean & lubricate as needed.
    Pay particular attention to where the firing pin engages the ramp section of the "Breech Bolt Sleeve".

    I appologize if these instructions are overly simple, just don't want to assume what one's knowledge level is.

     

    LR-WSM

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    Re: FN SPR Bolt issue

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body">Check and see if the second from the front scope base screw is a little too long and is sticking into the receiver. </div></div>

    I'm inclined to agree as I've seen this w/ Rem's but wouldn't the OP see a scratch or goroove or some other sign on the bolt head.
     

    rossneder

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    Re: FN SPR Bolt issue

    I think we have a winner!

    It looks like a tool mark on the bolt cam, question is can I smooth it out without causing more problems? [img:left]
    2ef5eux.jpg
    [/img]
     

    PLeighton

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    Re: FN SPR Bolt issue

    Yikes....

    If it isn't too deep, you should be able to work it out using a file shaped like this:
    feilenskizze9a.gif
    F302707.jpg


    To have FN take care of it, I'm afraid you are looking at replacing the whole rifle.
    If you go that route, be prepared to be without it for up to six months.
    (They may have improved their turn around times, but I haven't heard anything.)

    Good Luck...
     

    rossneder

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    Re: FN SPR Bolt issue

    Thanks Phil,

    It was one of the CDNN actions, that's probably why CDNN had it.
    Can you think of any reason that smoothing it out would cause problems? Looks like the case is fully extracted and that the remaining 10 degrees just aligns the lugs. Am I missing anything?

    Thanks
     

    LR-WSM

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    Re: FN SPR Bolt issue

    Wow, thats pretty rough. What exactly was that gouge catching on. Are the edges of the gouge raised causing a clearence problem with the shroud or safety? If that is the case, I'd just knock the edges down enough to clear and keep it lubed.

    Good luck
     

    PLeighton

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    Re: FN SPR Bolt issue

    If at all possible, please post up a close up of the surface.
    What it looks like from the photo is that the detent at the top of the cam may have been misaligned.

    When you open the action and you feel that positive engagement, that is the firing pin seating in the detent at the top of the cam.
    Is there more that one detent, or is there the detent at the top of the cam and then a machining mark on the cam surface?

    As long as the detent is in the correct place, you should be able to reshape the cam as long as you be sure to pay attention to keeping it straight.
     

    rossneder

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    Re: FN SPR Bolt issue

    I think I have it.

    There is a slight ridge a few degrees before where the detent and the firing pin align. I'll reshape the ramp right before the detent and polish the rest.

    Thanks again.