Seating Problem Help

Discussion in 'Reloading' started by Blacktail, Feb 16, 2008.

  1. Blacktail

    Blacktail Well-Known Member

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    I have an STW i have been tinkering with and have been seating it out to an OAL of 3.640" I know the OAL in the Nosler manual says a Max of 3.60 am i too far out? But more troubling is when seating the bullets i am getting different measurements. Anywhere from 3.640 to 3.543. How can this happen when the lock nut and everything is tight?
     
  2. piutemike

    piutemike Well-Known Member

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    I am no expert by any means and I have only been relaoding for a month with the help of the guys on the forum. That being said, I have logged every thing I've done, taken careful measurements and noticed that my bullets are not always the same length. I'm talking same bullets out of the same box. I also started with a cheap set of calipers that I did not think were repeatable in their measurements and bought a new pair.

    I'm sure somebody with more experience will have something more intelligent to add. A.J. Peacock on the forum has helped me quite a bit with his posts.
     

  3. 260shooter

    260shooter Well-Known Member

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    Blacktail

    It is likely your bullets. Your seating die seats the bullet off the ogive (SP) of the bullet. The base to ogive length is what you are concerned with. The overall length of your cartridge may vary some, .1 in your case is extreme. You might research to find out if your seating die seats the bullet off the ogive or bullet point. Get a bullet comparitor (sp) from Sinclair. This is far more accurate than measuring from base to bullet tip.

    260
     
  4. Blacktail

    Blacktail Well-Known Member

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    That definitely makes some sense. I just loaded up a set and tried to set the OAL at 3.645 and ended up with 5 of the 12 on the money and the others at 3.641 to 3.642. I will have to make a purchase. thanks
     
  5. britz

    britz Well-Known Member

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    There are three possible answers that I can think of. One is that bullets tips are not all the same. That is, bullets tips are not always exactly the same and can vary by a few thou if you are measureing off of the tip with a standard caliper. You need to use a stoney point or similar bullet comparator inorder to measure bullets correctly off the ogive.

    Two is that your tips of the bullets may be hitting the seater plug rather than the ogive of the bullet hitting the sides of the seater plug like they are supposed to. I have heard that the remady to this is to simply drill it out, but doing this risks creating a burr that will cause runout (I recently experienced that w/ a RCBS die)

    THree (which I feel would be a long shot, but possible) is that your press is sloppy or your stroke is inconsistant. Since a seater die is usually kept about .1" above the top of the stroke, you are relying on the stroke stop to make every bullet the same. If this is the case (if you are using an extremely cheap wore out press like a cheap Lee) than you could replace the press or make sure you are applying simalar pressure on each stroke.

    Most likely it is the first one, measureing wrong. It could be a combination of the first two.

    As far as your COAL goes, the SAAMI spec is just a reccomendation to ensure that it fits into all Magazines basically. The main things you need to know about seating is that seating next to the lands creates excess pressure and you should use caution doing this; consistent seating can make a huge difference in accuracy and POI changes from lot to lot; Many, but not all rifles shoot best seating very close to the lands (a few thou); and lastly that crimping isn't necessary in most calibers.

    Hope this helps ;)
    Mark
     
  6. AJ Peacock

    AJ Peacock Well-Known Member

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    +1 Britz, (you saved me a bunch of typing).

    AJ
     
  7. shootinfool

    shootinfool Well-Known Member

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    get a pair of stoney point masuring tools. they masure the length of the bullet from the ogive to the bottom of the case, which is what really matters. On some of the bullets that don't have a polymere tip they can actually get smashed in a little bit from bouncing around in the box as well as from the seater hitting the tip. If you get a pair of the stony point guages and a modified case of your caliber to fit them, then you can tell exactly how far out the bullet has to be to touch the lands and grooves and thus determine how much of a jump you want and where to set your dies to acheive this masurement from the ogive of the bullet to the bottom of the case.