Safe seating depth?

Discussion in 'Reloading' started by Jinx-), May 15, 2011.

  1. Jinx-)

    Jinx-) Well-Known Member

    Messages:
    693
    Joined:
    Aug 23, 2009
    I got 140 gr Nosler CC and 139gr Lapua Scenar bullets, the max OAL my chamber allows shown on the picture, I highlighted seating depth with black marker.

    [​IMG]
    Is it safe to seat bullets that far? Also I was looking to seat them more down like 0.015" and 0.030".
     
  2. boomtube

    boomtube Well-Known Member

    Messages:
    1,595
    Joined:
    Oct 8, 2007
    OAL/seating depth matters not if we develop our load at the depth we wish to use.
     
  3. Jinx-)

    Jinx-) Well-Known Member

    Messages:
    693
    Joined:
    Aug 23, 2009
    thing is I can't seat them any more further, at this point bullet bearing surface is pass datum line, to work load I will have to seat them more in.
     
  4. boomtube

    boomtube Well-Known Member

    Messages:
    1,595
    Joined:
    Oct 8, 2007
    "..thing is I can't seat them any more further, at this point bullet bearing surface is pass datum line, to work load I will have to seat them more in."

    I'm totally uncertain what you mean. But IF you "can't seat them any more further" I suppose you "will have to seat them more in" whatever you are refering to (In the case? In the lands?). Or change bullets. ?
     
  5. Jinx-)

    Jinx-) Well-Known Member

    Messages:
    693
    Joined:
    Aug 23, 2009
    Skip one word... No more further out. Generally with long bullets, is it safe to seat them way pass datum line or in the powder compressing powder that way?
     
  6. rscott5028

    rscott5028 Well-Known Member

    Messages:
    2,608
    Joined:
    Apr 18, 2010
    Yes. You can seat bullets past the datum line.

    The amount of jump to the lands is often a factor of accuracy. Varying the amount of jump is part of load development and can also affect pressures. Some rifle/bullet combos prefer a lot of jump and some prefer to be slightly jammed into the lands. Most like just a little .010". Either way, you need to start with minimum charges and work up to it.

    The degree to which the powder fills the case may also be a factor in accuracy. With too much empty space, the powder isn't always lying in the same location and doesn't necessarily ignite/burn as consistently as it might with a full case. Hence, different powders afford the option to better utilize case capacity while matching the most efficient burn rate, harmonics, etc.

    Compressed loads aren't inherently bad. But, they need to be approached and managed carefully and worked up to.

    When developing loads, you always need to factor in some safety margin. Increased ambient temperature will increase pressures. So, maximum loads developed in cold weather may create pressure problems when fired in hot weather.

    The "datum line" that I think you are referring to is for measuring headspace between that point on the shoulder to the bolt face. It really doesn't have anything to do with seating depth.

    You need enough bearing surface between the neck and bullet to hold it in place and to keep the bullet from falling out or wiggling. Seating the bullet any deeper is of no real benefit and only uses case capacity.

    Hope this helps.
    Richard
     
  7. Jinx-)

    Jinx-) Well-Known Member

    Messages:
    693
    Joined:
    Aug 23, 2009
    Thank you Richard, I never had to seat bullets that far down, but this is my MAX OAL now, I'm trying to develop load using this long pointy bullets and freebore in my chamber is a bit short so it raised safety concern, like pressure and such. Well now its all clear and I'll start my load development, no sweat :D