XCR Barrel Retaining Screw Question
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Thread: XCR Barrel Retaining Screw Question

  1. #1
    Newbie BazookaJoe's Avatar
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    XCR Barrel Retaining Screw Question

    I think its safe to ask this here...
    I'm the owner of a XCR-M, and I really love the rifle!
    Picked it up online, but the previous owner didn't supply a manual.
    Is there a "break in" procedure?
    Also, is it safe to replace the barrel retaining screw with that of a set screw (headless)? So the screw sits flush within the upper?

  2. #2
    XCR Guru fmunk's Avatar
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    Don't have manual for the -M, but I do have a old version armorer's course PDF for the -L; -M specific features is not covered. As for using a set screw, as long as it has matching thread specs, I don't see why not. In fact, I recall reading someone doing just that with their -L some years ago. Other than starting with more pressure and then working your way down. I don't think there are any special break-in procedures aside from the usual (lube and shoot).
    Fool-proofing serves only one purpose: identify bigger fools.

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    XCR Guru navalbeaver's Avatar
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    Quote Originally Posted by BazookaJoe View Post
    I think its safe to ask this here...
    I'm the owner of a XCR-M, and I really love the rifle!
    Picked it up online, but the previous owner didn't supply a manual.
    Is there a "break in" procedure?
    Also, is it safe to replace the barrel retaining screw with that of a set screw (headless)? So the screw sits flush within the upper?
    There's been a "break in" for the Ls, not 100% if there's one for the Ms. Usually it's a few hundred rounds on the higher gas settings. I'd argue that it may be unnecessary on some rifles but it's a CYA if RA let's some rough examples go from the factory. This is for general operation and isn't a "barrel break in" procedure.

    I've personally done the screw swap for a set screw. It's a bit sleeker but you end up with a smaller Allen head to get the torque on the screw and there was some discussion about the finishing done to the tip so that it engages the dimple in the barrel extension evenly. I thought Terra had said they actually finished them up to get better engagement than you would from a hardware store screw. YMMV and you can probably finish one yourself if you really want the set screw to work.
    Last edited by navalbeaver; 03-19-2017 at 06:39 PM. Reason: Damn autocorrect

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    Newbie BazookaJoe's Avatar
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    Thanks for the info!!
    Hope you don't mind if I pick your brains...
    What is the torque of the bolt?
    Also, here are a few pics of the set screw:

    XCR Barrel Retaining Screw Question-ce27e1q.jpg

    XCR Barrel Retaining Screw Question-g4kzlmg.jpg

    XCR Barrel Retaining Screw Question-0z1mwsg.jpg

    Your saying that the tip would have to be filed to a tip?

  6. #5
    XCR Guru navalbeaver's Avatar
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    I think 200in/lbs is in the manual but have heard up to 240-250. Other recommendations include "hand tight" then a quarter turn.

    I usually do 240. It's easy to read on my cheap ass torque wrench.

    I'm not saying it "has" to be filed down but I'm pretty sure it was Terra relayed here in the forum that they did do some work to the barrel bolts in order to increase the contact surface. Look at the barrel bolt and the dimple in the extension. Without working on the set screw, you're only going to get shallower engagement and only on the outer edge of the dimple.

    Whether or not this actually matters..... I don't know.

    The perceived benefits ultimately weren't worth it for me and I went back to stock.

    Again. Not sure if the above actually has any effect on the rifles performance or durability.

  7. #6
    XCR Guru fmunk's Avatar
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    Armorer's course for the the -L says hand tight then +70 degrees. IIRC, there were reports of helicoil coming loose when they tightened to 240-250. Could have been an out of spec wrench too. Common with the cheap ones.
    Fool-proofing serves only one purpose: identify bigger fools.

  8. #7
    XCR Guru navalbeaver's Avatar
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    Some threads from the grave. Manual says 200 back to 2009. Terra seems to have said 200 should be good but also recommended 250 if you can get it.

    Problem with barrel bolt loosening. (200 in the manual, 250 in the field)

    Anyone use Nord Lock washers on the barrel bolt? (talks about the bolt itself on page 3, 200-220)

    Barrel bolt question (bravo has a couple of good posts talking about the screw mod)

    Word of Caution: Broke My Bbl Bolt This Evening. (one of Sean's odysseys with the XCR)

    Snapped barrel retention bolt. (more recent, 200 in the manual, 250 from bravo/Terra)
    Last edited by navalbeaver; 03-20-2017 at 08:12 AM.

  9. #8
    Newbie BazookaJoe's Avatar
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    Thanks for all the info!!

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    Expert Mechanic's Avatar
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    Quote Originally Posted by BazookaJoe View Post
    Thanks for all the info!!
    Note that I have used pan-head type socket screws as a replacement. I cut them to a length so they torque out just before the head bottoms to ensure it's applying pressure on the barrel extension. All you really need to worry about is getting a good symmetric taper so you're not moving the barrel closer/further relational to the bolt so you're not affecting headspace in battery. I taper the tips by hand on a grinder. There's some pics floating around here somewhere.

    I like a magwell grip and the panhead is easier on the knuckles!
    "Don't Tread On Me!"
    -- (reiterated without permission) Rich Hornay

  11. #10
    XCR Guru fmunk's Avatar
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    Your mileage may vary. Personally, a better solution is to run a vertical grip a couple inches forward of bolt. Close enough to a magwell grip for comfort, and further forward to give your rifle a better more stable platform. And, most importantly, you leave the Alex specified hardware well alone in case you ever need to make a related warranty claim.

    Another reason to leave it alone: how dare you question the intention of the XCR God himself (that's a joke).
    Fool-proofing serves only one purpose: identify bigger fools.

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