Belted vs. non-belted for accuracy.

Discussion in 'Long Range Hunting & Shooting' started by 25792SP, Aug 6, 2009.

  1. 25792SP

    25792SP Member

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    While watching a David Tubb video recently, he stated that one of the reasons a 6-284 is an accurate round is because it is not a "belted case". Because David didn't, can someone here possibly explain how the belt on a magnum case causes decreased accuracy?
     
    Last edited: Aug 6, 2009
  2. AJ Peacock

    AJ Peacock Well-Known Member

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    I don't think anyone will be able to do it. I hate to appear to disagree with "David Tubb", but I don't think it makes a hill of beans whether a cartridge is belted or not from an accuracy perspective; when comparing cartridges of equivalent capacity.

    Maybe I'm wrong, someone will certainly straighten me out if I am.

    AJ
     

  3. Autorotate

    Autorotate Well-Known Member

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  4. johnnyk

    johnnyk Well-Known Member

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    You're not wrong at all AJ. The "speculation" or "theory" behind the non-belted cartridges being more accurate, was that to establish standards for measuring and maintaining headspace, a dimension is specified between the bolt face and a reference point, called the "datum line". For rimless, semi-rimmed and rebated cartridges (.284 family), the datum line is established at a point on the shoulder. For non-belted cases this is roughly half-way the shoulder where it rest against the chamber. The datum line for belted magnums is the forward edge of the recess provided for the belt.
    I guess they (nay-sayers) figured that since the belted mag cases headspace off the recess in the chamber that the front end (bullet end) just flops around up there in the forward part of the chamber.
    This "problem", as it's perceived, can be overcome with a properly adjusted die. To do this, unscrew the die a full turn and run a smutted, fire-formed case into the die chamber. You should be able to detect a mark where the case neck stopped inside the die neck cavity. Screw the die back down until the die shoulder is in firm contact against the case shoulder. Reload a couple of "dummy" rounds and chamer them in your rifle. You should be able to feel a slight pressure caused by contact of the shoulder. Wa-La, now you have a belted magnum case headspacing the same as the "more accurate" non-bleted. Hope this helps. JohnnyK.
     
  5. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Thats funny since Davids long range 30 cal is based on a full length belted magnum case very similiar to the 300 Jarrett which is basically a 300 Wby Mag with conventional shoulder angle.....

    In theory, the belted magnum case headspaces off the forward edge of the belt. That may be somewhat factual with firing virgin cases but once a case is fired in a chamber, if it is resized properly, that case will headspace off the shoulder just like any non belted cases so the belt becomes a totally non functional part of the case and has no effect on accuracy of any kind, good or bad.

    That said, If a chamber is set up to tightly for a belted magnum, some cases may bind solidly on the chamber in the belt area and this WILL cause severe accuracy problems. This is generally only seen in custom rifles where the maker is not accustomed or aware of this danger. You simply can not chamber a belted magnum as short in headspace as you can a non belted case. As such, you have to allow for the variation in in the belt thickness in the chamber depth.

    So, that first firing may not be quite as accurate as a non belted magnum but again, once the case is fired in the chamber and if the case is sized properly, the belt is a dead topic, no function at all good or bad concerning accuracy.

    One final thought. The chambering in the rifles David Tubbs used to win all of his championships had very little to do with him winning, it was far more his skill and talent then the chambering, barrel or complete rifle he was using. I have never been a firm believe in inherent case design as far as one being more accurate then another. Some chamberings are easier on the complete rifle system and some are easier to tune mainly because of lower levels of performance but in the end, its hard to say one design is more accurate then another when both are similiar in case capacity, pressure and velocity.

    Just my opinion and everyones got one of those.
     
    Last edited: Aug 6, 2009
  6. J E Custom

    J E Custom Well-Known Member

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    Well it sounds like its unanimous about the belted cases compared to non belted.

    My opinion is the same, for what it's worth. Brass quality and head space are the
    most important issues with the belted cases,

    I competed with the tubbs family and these guys were very very good !!! so skill had
    the most impact on there success (Every one Has a bad day but these guys seldom
    did).

    When setting up a belted case there are different rules as kirby said. But once they are fire
    formed the rules for reloading should be the same.

    Actually the non belted cases are more user friendly (A computer geek term) They feed easy,
    size easy, head space easy,uniform easy, Whats not to like.

    Just my humble opinion

    J E CUSTOM
     
  7. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    Belted cartridges are just as accurate as any. On the longest shots thread a guy shot a groundhog over 2000 yards with a 338-378 wby and numerous long range deer. I have killed a lot of stuff to over 1300 yards with belted magnums including my 338-378's. I would not let a belt deter me from my cartridge choice.
     
  8. PKeller

    PKeller New Member

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    AJ and the opinions that follow are correct. I have extensive knowledge in this particular topic.

    Suffice it to say, whether the cartridge is belted or not, any custom rifle maker headspaces off of the shoulder, not the belt. Sure when the belted magnums first came out( decades ago) they were headspaced off of the belt. I have no idea what the factories are doing now, my guess is the cheapest thing.

    Hope this helps.