300 WSM, 300 WIN MAG FREEBORN

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by BOB LEE SWAGGER, Jul 17, 2017 at 10:13 AM.

  1. BOB LEE SWAGGER

    BOB LEE SWAGGER

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    It' seems pretty easy to find freebore recommendations for the 300 WSM. .200-.220 for the 200-215's and .280 for the 230's. Please tell, your thoughts on freebore for the 300 WIN MAG.

    Spell check chose freeborn, not sure how to change header!!!
     
  2. sdean

    sdean

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    I don't think the freebore knows what cartridge is behind it. Should be the same.
     
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  3. Cody Richardson

    Cody Richardson Silver $$ Contributor

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    I have a WSM and Win mag both throated at .280 for the 230's. Both shoot great!
     
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  4. XTR

    XTR

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    There is a variable as it were is cases with shortish necks (like the 300WM). They are more limited as to what is "ideal". Ideal being defined here as the bottom of the bearing surface somewhere in the middle 1/3 of the neck.
     
  5. Steve Blair

    Steve Blair

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    I've recommended .310" for 230's in .300 WM since the neck is .030" shorter than .300 WSM. That allows up to .030" seating off the lands and/or avoiding any internal ridge (AKA donut).
     
  6. Bart B.

    Bart B.

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    SAAMI specs for tha 300 Win Mag shows freebore length at zero. Rifling lands start at the chamber mouth .315" diameter then taper down 1 deg 26 min 32 sec angle to .300" bore diameter.

    Freebore is the chamber constant diameter from the chamber mouth to the origin of the rifling where the tapered throat (leade) starts.
     
  7. BOB LEE SWAGGER

    BOB LEE SWAGGER

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    If I say that to the pros at JGS I think that they will say the same thing that I do.

    Huh? What reamer specific freebore do you want?
     
  8. dkhunt14

    dkhunt14

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    If you are a long-range shooter you will not be a very HAPPY CAMPER with a zero freebore. Matt
     
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  9. Terry_M

    Terry_M

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    Is freebore indicative of "bullet jump" from seated length to engaging the lands? Does freebore change as throats erode?

    ETA: When I read the title of the thread I thought there may be a new wildcat coming out ;)
     
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  10. XTR

    XTR

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    As noted above, freebore is the portion of the bore in front of the neck where the reamer removes the rifling and leaves a smooth section at groove diameter. It determines how far out of the case you can seat the bullet before you touch the lands.

    If the freebore is very short you will be forced to seat long bullets well back in the case in order to chamber the loaded round.

    If the freebore is overly long you will not be able to reach the lands and the bullet will be forced to jump.

    The "ideal" freebore for a particular bullet will allow the reloaded to seat the bullet touching the lands and have the bearing surface of the bullet end somewhere in the middle 1/3 of the neck. This will allow the reloaded to seat his bullets in a way that gives the best accuracy (jumped or jammed) with out having the bullet taking up space in the case for powder.

    Note that "ideal" for a 230 is not the same as for a 185. One bullet is much longer than the other. In the case of custom rifles we often choose a chamber that is ideal for the bullet we intend to shoot.
     
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  11. Bart B.

    Bart B.

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    Freebore is a few thousandths larger in diameter than bullets. There's a few thousandths spread allowed in SAAMI specs for both bullets, freebore and groove diameters. Freebore doesn't lengthen per se like leades do but it can erode in all directions. Reamers and barrel makers are not bound to adhere to SAAMI specs.
    That's about one-fourth of what determines where bullet ogive touches bullets. Other dimensions involved are leade angle, bullet diameter & shape and groove diameter. Leade erosion over time lessens its angle.

    That myth (news to me) is the same as the popular myth saying the bullets heel should be at the neck-shoulder juncture. How come it's not mentioned in load data given by top ranked match winners and record setters to others that publish them?
     
    Last edited: Jul 18, 2017 at 6:50 PM
  12. BOB LEE SWAGGER

    BOB LEE SWAGGER

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    I was hoping for numbers to take to a reamer maker. That's all. The title is not WTF is freebore?
     
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  13. dkhunt14

    dkhunt14

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    I like the pressure ring in front of the neck shoukder junction. I have seen it mentioned very many times. Most good gunsmiths and reamer makers know what works and they just use it. Some of the best match shooters won't tell becuase they dont want to take bashing from the keyboard pushers. Matt
     
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  14. tuttlefarm

    tuttlefarm

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    Bob, I was shooting the 210 Hunt VLD, my freebore was .255..... It shot well enough to hang with some of the best
     
  15. BOB LEE SWAGGER

    BOB LEE SWAGGER

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    For the 300wm?
     
  16. tuttlefarm

    tuttlefarm

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    Sorry Bob, No..... the WSM.... the neck of the WM is .035 shorter than the WSM. So if I were specking out a reamer it would have a .290 freebore
     
    Last edited: Jul 19, 2017 at 7:34 AM
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  17. BOB LEE SWAGGER

    BOB LEE SWAGGER

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    I'm confused. Or an idiot! I thought that the short neck of the WM mitigated a longer freebore. You're saying for 210's it's .255 for the WSM & 220 for the WM?
     
  18. sdean

    sdean

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    Seat the bullet you want in a case and send it to JGS. Done
     
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  19. BOB LEE SWAGGER

    BOB LEE SWAGGER

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    I did that before on another cartridge and was about 100 thou longer than any I had been advised. The level of the empirical guidance here is still of great help.
     
  20. Steve Blair

    Steve Blair

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    Is that you, Frank? o_O
    You have it right. The shorter neck needs longer freebore for the same bullet. A cartridge like the 6mm Remington, with a relatively long neck, allows a lot of seating flexibility. Typical case necks that are one caliber or less, not so much.
     
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