Gunsmithing Installing arca on fiberglass stock

stello1001

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Hey all,

I've got a couple win70 rifles. I also have a spare SPR stock that I am probably going to bed my 223 heavy varmint into. I wanna go arca with it, heck I want to convert all my rifles into arca.
Anyhow, I wanted to use the Action screw to install the rail. The original HS stock would work great in such a way, pictures below, but I don't want arca on that particular stock. For the SPR stock, which isn't flat all the way, how should I go? Am I overthinking this (like most gun related stuff 😂😂) and just move the rail forward a bit and drill the stock in two locations? How are you guys going about this?

I should also mention that I plan on converting to AI style mags but that shouldn't intervene with arca placement.
 

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KnowNothing256

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    Wouldn’t you need to get a longer action screw if you wanted to use that location to mount the ARCA?

    I mounted mine forward of the front action screw, drilled the stock in enough places to use all three mounting screws provided by the rail mfg (Henderson). On the Bergara HMR stock that ended up being one new drilled/tapped hole plus the original two sling stud locations. On the CZ 455 it was three new holes with T-nuts.
     

    stello1001

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    Wouldn’t you need to get a longer action screw if you wanted to use that location to mount the ARCA?

    I mounted mine forward of the front action screw, drilled the stock in enough places to use all three mounting screws provided by the rail mfg (Henderson). On the Bergara HMR stock that ended up being one new drilled/tapped hole plus the original two sling stud locations. On the CZ 455 it was three new holes with T-nuts.

    The screw pictured above is just to show it fits really nice in the rail screw inlet. I have multiple extra action screws for these rifles in all sizes.
     

    KnowNothing256

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    The screw pictured above is just to show it fits really nice in the rail screw inlet. I have multiple extra action screws for these rifles in all sizes.
    Fair enough. You’re gonna have to jump through a couple hoops to make it work properly, I think; you’ll likely need a spacer between the rail and the bottom metal to make sure the action screw tension is properly transferred metal to metal all the way up to the receiver. Don’t see any reason it can’t work, but it’s certainly not how the bottom metal is intended/designed to work.
     

    stello1001

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    Fair enough. You’re gonna have to jump through a couple hoops to make it work properly, I think; you’ll likely need a spacer between the rail and the bottom metal to make sure the action screw tension is properly transferred metal to metal all the way up to the receiver. Don’t see any reason it can’t work, but it’s certainly not how the bottom metal is intended/designed to work.

    I may just have to move it up a few inches and screw the whole rail onto the stock.

    I was simply asking because AREA419 has a how to video on the installation of their arca rails. They use the action screw and honestly, i like that idea. However, my stock is not entirely flat.

    Just trying to weigh my options.
     

    KnowNothing256

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    I may just have to move it up a few inches and screw the whole rail onto the stock.

    I was simply asking because AREA419 has a how to video on the installation of their arca rails. They use the action screw and honestly, i like that idea. However, my stock is not entirely flat.

    Just trying to weigh my options.
    My CZ 455 stock is slightly rounded on the bottom, I just ran with it. Alternatively, you could bed the rail to the bottom of the stock if there was concern about insufficient contact, wouldn’t be too hard. Most difficult part would be keeping the mounting screws out of the gloop.
     

    stello1001

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    Seems weird to pull the rail every time you want to remove the bottom metal. T-nuts in the barrel channel seems like a better option.

    The 2 videos from Area419 that I've seen demonstrating how to install the rail are both installing it on the action screw. I guess this is what led me to believe I should do it like this too. However, I'll probably just move it further and use the area that's 100% flat. Either way, who's taking off and putting back on their bottom metal? I've literally never had to do that...
     

    KnowNothing256

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    The 2 videos from Area419 that I've seen demonstrating how to install the rail are both installing it on the action screw. I guess this is what led me to believe I should do it like this too. However, I'll probably just move it further and use the area that's 100% flat. Either way, who's taking off and putting back on their bottom metal? I've literally never had to do that...
    I do it every time I pull the BA out of the stock. Some folks go so far as to take their barrels off to clean them. Doesn’t happen all the time, but it’s not never either.
     

    Statusquo

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    Sawtooth Rifles makes an mlok rail to inlet in your stock. This is a HS stock for a long action Mode 70. Side note, I did some modifications so it takes AI mags, too .

    C6C0BE5B-6661-453E-A969-F4D70FC083DD.jpeg
     

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    stello1001

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    I do it every time I pull the BA out of the stock. Some folks go so far as to take their barrels off to clean them. Doesn’t happen all the time, but it’s not never either.

    I suppose that could be true for some other people too. I do take barreled action out every now and then. The bottom metal is attached to the stock via the two action screws so it falls off but it's not that I'm wanting to take it off.

    And as far as taking the barrel off, I don't tools or equipment for that. And my rifles are factory rifles, they don't have switch barrel setups.

    Although i gotta say, it would be very convenient to be able to take off my barrel, plug the chamber end, fill with CLR, and let it hang over night in order to clean and remove carbon rings.

    Sawtooth Rifles makes an mlok rail to inlet in your stock. This is a HS stock for a long action Mode 70. Side note, I did some modifications so it takes AI mags, too .

    View attachment 7752014

    This is pretty interesting, I will look them up.
     

    buffalowinter

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    My action screws only tighten onto their pillars. I never have bottom metal or rails as part of the action bedding. I drill out clearance holes for the action screws in the bottom metal/rail and bed the bottom metal/rail separately.
     

    mick243

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    Sawtooth Rifles makes an mlok rail to inlet in your stock. This is a HS stock for a long action Mode 70. Side note, I did some modifications so it takes AI mags, too .

    nice - very interested to hear what mods you did to make it take AI mags (I have a short action that is currently a blind mag...)
     

    stello1001

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    nice - very interested to hear what mods you did to make it take AI mags (I have a short action that is currently a blind mag...)

    No mods as of yet...
    The MDT AI mags should work with win70 rifles without having to open up the action. I have an MDT chassis coming in and various different MDT mags. If I can't get it to work with the 223 I should be able to with the 308. Even if slight modifications to the mags are needed. I'll find out soon.
     

    Statusquo

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    nice - very interested to hear what mods you did to make it take AI mags (I have a short action that is currently a blind mag...)
    I had my action cut for a Wyatt’s box previously. Ordered PT&G bottom metal, but rather than cut into the lug recess, I cut the bottom metal b/w the trigger and box and welded it up to line up with normal m70 magazine. A little more opening up was needed to the rear. Feeds flawlessly and didn’t have to monkey around near lugs.

    If I had to do it again, I’d just buy a mausingfield.
     

    Secant

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    I’ve installed several arca rails in my carbon stocks recently. For what it’s worth, manners strongly recommended against using the action screw. I just installed t-nuts forward of the action.