Above Max COAL to hit lands

Discussion in 'Reloading' started by j_unzicker, Dec 8, 2010.

  1. j_unzicker

    j_unzicker Well-Known Member

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    Hello,
    I am new to this forum, and this is my first post. I hope you guys can help me.
    I am reloading for a Rem 700 7RM using the 168 VLD Bergers and I am trying to find the right COAL before I tweek too much with different charges. I ran a bullet partially down the neck of the cartridge in my press and then I used the bolt in my gun to push the bullet up against the lands. I pulled the seated bullet out and took measurement 3.460". I know that the recommended max COAL for this cartridge is 3.290, so my question is, "Can I safely shoot at 3.460?" I would like to seat at the following depths and compare accuracy: 3.450; 3.400; 3.360; 3.330. What are your thoughts?
    Thanks.
     
  2. Take the measurement multiple times to ensure you have an accurate measurement. Then measure your mag - there's no use loading rounds that won't fit in your mag. Then, if you still have a long measurement load up your rounds to whatever it need be, just keep an eye on pressure signs like a sticky bolt handle and flattening primers. It's not uncommon for a guy to not be able to seat them really close to the lands because they just won't fit in the mag.

    If you have a chronograph use it and compare your velocity to the book's velocity for that load and you'll get an early idea on how much more you can safely push it.
     

  3. Gene

    Gene Well-Known Member

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    Miller has it right. But - Do Not seat bullets so long that they remain in the chamber when you remove a unfired round. You will disable the rifle; powder all over the place and bullet firmly in the lands. I seldom read the reloading manuals recommended COAL if my rifle has a magazine, because they must feed thru it. And get a Hornady comparator tool and start measuring OAL from the base to ogive. Much more accurate. Bullet dimensions vary considerably.
     
  4. BigSkyGP

    BigSkyGP Well-Known Member

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    Before you get too far read 1-5: Hand loading for Long range 1: brass case prep - Sniper's Hide Forums

    This guy is a match shooter, and this is his reloading manual. It all made great sense to me. I wouldn't worry about them fitting in your magazine, accuracy comes first. You can always go back to magazine length if you want/need to. COL is SAMMI guideline for rifle/ammo manufactures. COL is a starting point, or end point depending on how you look at it.
     
  5. Boss Hoss

    Boss Hoss Well-Known Member

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    In short COL will not work for this. Each bullet is or can be a different length. To do this correctly you will need to know the bearing surface measurement, sort the bullets then set the COL.

    COL has nothing to do with when the bullet touches the lands.
     
  6. j_unzicker

    j_unzicker Well-Known Member

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    Thanks, guys.
    I was a little surprised to find out that I can jam the lands and still fit the cartridge in my Rem 700 magazine with room to spare, so I was happy about that. I'm glad to know that I wouldn't be breaking a cardinal rule. I think I will start by loading various charges (starting low) seating the bullet about .005" from the lands. My undersanding is that this is about the distance that will put the most pressure on the load. Then I will shoot just to evaluate pressure signs. Then when I feel confident about the pressure at any given charge, I think I will work to adjust the COAL at that charge to find the sweet spot. Then using that COAL, I will go back and tweet the charge amounts to find the most accurate load.
    Am I missing anything? Any other suggestions?
    Thanks.
    BTW - I did just get an Chrony F-1 for an early Christmas present, so I will put it to good use. I am hoping that my most accurate load will put me around 3000f/s, but we shall see--accuracy is most important.
     
  7. ScottB

    ScottB Well-Known Member

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    The link you provided was a great read....thanks!


    Scott
     
  8. Loner

    Loner Well-Known Member

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    COAL is minimum length not maximum. If you seat the bullet shorter you can up pressures. The bullet manufacturer is the best source for COAL.
     
  9. j_unzicker

    j_unzicker Well-Known Member

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    OK...I set my bullet on the lands and climbed the ladder (as described in the article). I loaded rounds charged from 60.5 - 64 grains of IMR4831 (7RM). Starting with 60.5 grains my bullets climbed up the paper as the charges increased and they climed in velocity about 60 f/s for every grain added. Until I reached 62.5 grains. Then they started dropping lower, until I shot the 64 grain charge. My velocity climbed 120 f/s and the shot was about 4 inches higher than my highest shot. Primer looked OK and I didn't feel a tight bolt, but I am assuming that this is my gun saying that's enough powder.
    I will take the next step and vary my charges between 61 - 63 grains with increments every 2-3 tenths of a grain and see how that ladder looks.
    I really like this method. Saves bullets and time. I don't have to worry about groups until my gun tells me that I have found the right charge...then I will play with the COAL.
     
  10. Gene

    Gene Well-Known Member

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    Loner - Seating the bullet lower will not increase pressure. Seating it longer will.

    In simple terms: If the bullet is seated long jammed into the lands, it requires more "push" to get it moving, ergo more pressure is generated. If the bullet ogive does not touch the lands, it has "jump" to release the pressure before it engraves.
     
  11. BigSkyGP

    BigSkyGP Well-Known Member

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    > I think it can go both ways. Starting on the lands is a more definable variable to start with.

    Think of a steam engine with a full head of steam just building speed then slowing due the restristion. Only the full head of steam causes the steam to build higher pressure because of the sudden slow in the push. Smokless powder is really a modern form of dinamite, the more pressure/resistence the faster it burns. Wierd stuff, but quantifiable.
     
  12. Troutslayer2

    Troutslayer2 Well-Known Member

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    If you were compressing the powder by seating deeper it could cause higher pressure, I think?