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Thread: Free bore

  1. #1
    Join Date
    Jun 2005
    Location
    Concord,NC
    Posts
    53

    Free bore

    What Dia should the free bore of a 6mm be ? how much larger than the bullet ? If so by how much ?
    Thanks for your comments .

  2. #2
    Join Date
    Feb 2003
    Location
    SW Kansas
    Posts
    749

    For short range BR

    I like .2438 lots of reamers ground for .2435 however. Main thing is having the freebore bigger than the bullet by a few tenths or so.

    Richard

  3. #3
    Join Date
    Sep 2003
    Location
    Oriental, NC
    Posts
    970
    The main thing is to have a freebore diameter larger than the groove diameter of the barrel.
    .0005" doesn't always get you there.

  4. #4
    Join Date
    Jun 2010
    Location
    USA
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    646

    Thumbs up

    Quote Originally Posted by Dave Tooley View Post
    The main thing is to have a freebore diameter larger than the groove diameter of the barrel.
    .0005" doesn't always get you there.
    Roger this, Dave! I just finished a barrel for a pal - first barrel I've done on which the 'free-bore' portion, of a proven reamer (.2046" free-bore Dia.), never touched the groove(s) . . . I reckon, by the Hawkeye view, it's a ZERO free-bore, 1.5 Deg. "throat" !??! It's not a BR type of [button-rifled] barrel, but of good repute, I was/am surprised at the large groove diameter, while the bore was 'normal' - it's 20 Cal. Seeing how it performs is going to be interesting - I'm betting on up to the standard of < .5MOA . . . I hope - its just for prairie dogs and coyotes! RG
    Last edited by R.G. Robinett; 09-22-2020 at 11:46 PM.

  5. #5
    Join Date
    Jun 2005
    Location
    Concord,NC
    Posts
    53
    My mics I feel are pretty good and on my reamer I'm getting a read of .2436 . What do you think ? I know all mics are not the same even if they check right on the gauge . My barrel had .237 stamped on the end of it and I don't have a way to check it .
    Last edited by ArtinNC; 09-22-2020 at 10:45 AM.

  6. #6
    Join Date
    Feb 2003
    Location
    SW Kansas
    Posts
    749

    take the drop from the muzzle

    Quote Originally Posted by ArtinNC View Post
    My mics I feel are pretty good and on my reamer I'm getting a read of .2436 . What do you think ? I know all mics are not the same even if they check right on the gauge . My barrel had .237 stamped on the end of it and I don't have a way to check it .
    end of the bbl and true the OD, make sure your not in the lapping bell portion Run the reamer in to just cut the freebore-throat. You can see from that everything you need to know without measuring tools.

    Richard

  7. #7
    Join Date
    Jun 2005
    Location
    Concord,NC
    Posts
    53
    I had to cut the free bore longer , my chamber reamer was a 6mmBR with a .080 free bore for 65 gr bullets and I needed a .115 free bore for now for 105 gr bullets , and I may have to open it to more . And the .2436 dia I wish was bigger but that means another reamer , I'll have to see how it shoots first .

    Thanks for the comments .

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