Reloading term: off the lands?

Discussion in 'The Ammo & Reloading Forum' started by Spanky, Oct 16, 2009.

  1. Spanky

    Spanky New Member

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    When someone says "seating is on the lands" or "seating is .0XX off the lands", what are they talking about?

    Thanks
  2. williamd

    williamd New Member

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    The bullet is that far from touching the lands. I seat one die turn from the lands .. so 1/14 inch. Lowers pressure a bit but I do it as I get better accurcy. However, I have never gotten great accuracy from free-bore rifles - those have some open area before rifing starts. As on Weatherby Mk V's and Schultz & Laersn's I have owned.
    Last edited: Oct 16, 2009
  3. 312shooter

    312shooter Active Member

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    Barrel rifling consists of "lands" and "grooves" - accuracy is typically best when the bullet is juuuust about to touch the beginning of the lands, rather than jumping down the chamber before engaging the rifling.
  4. LDBennett

    LDBennett Well-Known Member

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    For best accuracy (not always, though, as some guns like a run on the rifling, but usually) it seems that getting the bullet close to the point in the barrel where the rifling starts is best. Some gun, like 22's with match chambers, actually slightly drive the bullet into the lands with bolt closure. This should not be done on any centerfire gun, though, as the pressures can get excessive if the bullet is delayed in leaving the case of the cartridge.

    The barrel is rifled and that means there are grooves and lands. The lands stick up proud the length of the barrel. There is a chamfer just ahead of the barrels chamber. The nose of the bullet normally is in this portion of the barrel when the bolt is fully closed. The shallower you seat the bullet into the case the closer the bullet gets to to the beginning of the lands of the rifling. There is a point, different for each bullet shape, where the bullet just touches those lands. Seating it there is problematical because the bullet can not be held stationary during the first of its motion or the pressure will build too fast and too high causing an excessive pressure situation. So for maximum accuracy the bullet is seated a small amount (typically a few thousandths of an inch) off just touching the lands. Or you may choose to explore other bullet positions to allow the bullet to get a run on hitting the lands. The point where the bullet just touches the lands is the reference point and is used to measure the run the bullet has on the rifling before hitting it. It is not uncommon for some guns to like as much a 0.060 inches off the lands or to like 0.001 inches off the lands. Only testing answers the question.

    Finding the point where the bullet is just touching the lands requires special tooling if you expect to find it accurately. It is an advanced reloading technique, best left for advanced reloaders. Jamb the bullet into the lands and you may get to find out what high pressures do to the gun.

    LDBennett
  5. Spanky

    Spanky New Member

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    Thanks all.
    LD, thanks for your detailed response. You answered what would have been my next question; how do you determine the length at which the bullet will touch the lands?
    I am no expert so I will keep my COAL a little below the maximum for now.
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