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  1. #1
    Super Moderator Rory McCanuck's Avatar
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    How to Determine Proper Bullet Seating Depth for YOUR Gun

    How to Determine Proper Bullet Seating Depth for YOUR Gun
    March 29, 2017


    Tools:

    A cartridge case that has been fired in your gun, and not resized.
    A bullet of the type to be used, with a full, undamaged nose.
    Calipers.
    A dark felt-tipped marker.

    Process:
    Step 1

    Insert the bullet into the neck of the fired case. It should fall freely into the case, with no resistance.
    Step 2

    Remove the bullet from the fired case and press the case neck lightly on a flat surface to create a small indentation or flat surface in the case neck so that it will grip the bullet.
    Step 3

    Insert the bullet, base first, into the case so that the case just grips the bullet by itself. Just get the bullet started into the case—don’t seat it too deeply.
    Step 4

    Completely color the bullet with the marker.
    Step 5

    Gently insert the case and bullet into the chamber of the firearm, and close the action. Do not pull the trigger.
    Step 6

    Carefully open the action and gently remove the case.
    Step 7

    Retrieve the bullet. It will either be stuck up in the lands of the barrel or still in the case. If the bullet is stuck in the lands, it can be removed by tapping the butt of the gun on the ground. Or, it can be dislodged by gently pushing it out with a cleaning rod. If the bullet is still in the case, then gently remove it with your fingers, taking care not to mar the ink, and proceed to step 8.
    Step 8

    During Step 5, the lands will have contacted the bullet and pushed it back into the case, causing the case neck to scrape the ink off of the bearing surface of the bullet. Simply push the bullet into the case until the edge of the case neck is just to where the ink has been scraped off.
    Step 9

    Carefully measure the overall length of the dummy cartridge. This overall length is called your “rifle seating” depth. It is where the bullet contacts the lands of the barrel. This length is different for every different type of bullet, as it depends upon the shape of the ogive (the taper) and the meplat (the tip of the nose) of the bullet. This process should be repeated three or four times to obtain a consistent average.
    Step 10

    A. Set your seating die to seat at a depth between .015 and .03 inches less than your rifle seating depth.

    B. Lightweight bullets may need to be seated further from the rifling. A depth of one bullet diameter inside the case neck gives good alignment and neck tension for ignition.

    C. The overall length must be short enough to function through the magazine.
    Don't blame me, I didn't vote for that clown. Oct 20, '15

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  3. #2
    Canadian ForcesMember 6MT's Avatar
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    ...or just purchase the Hornady OAL guage and the proper modified case. Follow instructions.

    sorry

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  5. #3
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    I used to worry about seating depth until I started using Quickload and now just seat to fit the magazine and tune the powder charge.

  6. #4
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    Quote Originally Posted by 6MT View Post
    ...or just purchase the Hornady OAL guage and the proper modified case. Follow instructions.

    sorry
    That cost money, not time.

    And won’t be available when world collapse has killed off shopping opportunities but not the Internet connection.

  7. #5
    Senior Member
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    Quote Originally Posted by 6MT View Post
    ...or just purchase the Hornady OAL guage and the proper modified case. Follow instructions.

    sorry
    THIS.

    The method in the OP is extremely inaccurate and likely to result in the wrong measurement.



    Quote Originally Posted by WSA View Post
    I used to worry about seating depth until I started using Quickload and now just seat to fit the magazine and tune the powder charge.
    Powder charge has nada to do with bullet seating depth. Bullet seating depth is all about reducing jump to the lands for better accuracy. Mag length loading ensures a GIGANTIC accuracy killing jump to the lands and depending on bullet shape it does not preclude the bullet being jammed into the lands and the resulting overpressure.

  8. #6
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    You can save yourself a lot of trial and error time by just setting your OAL to the Max given in your manual. The whole off-the-lands thing is nothing more than a load tweaking technique done after you've worked up the load. It's not necessary.
    Step 7 tells you nothing at all.

  9. #7
    Super Moderator Rory McCanuck's Avatar
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    Don't blame me, I didn't vote for that clown. Oct 20, '15

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  11. #8
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    Quote Originally Posted by Suputin View Post
    THIS.

    The method in the OP is extremely inaccurate and likely to result in the wrong measurement.





    Powder charge has nada to do with bullet seating depth. Bullet seating depth is all about reducing jump to the lands for better accuracy. Mag length loading ensures a GIGANTIC accuracy killing jump to the lands and depending on bullet shape it does not preclude the bullet being jammed into the lands and the resulting overpressure.
    Yup, I used to subscribe to that belief too. Used to just “kiss” the lands, or come very close-assuming it would fit in the magazine.

    Now I use science to predict optimal conditions including pressure and barrel time, and make small powder adjustments to fine tune accuracy.

    And powder charge absolutely has a relationship to seating depth.

  12. #9
    Canadian ForcesMember 6MT's Avatar
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    ....

    Sorry again. My mommy told me if I didn't have anything nice to say, then I should keep my big mouth shut.

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  14. #10
    Member Great White Hunter's Avatar
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    Hi Rory,

    Interesting, but for me, a newbie at reloading, is it good to be more consistent with overall length and power charge? I have not yet got out to check my loads, but our range opens May. I can;t wait to get out.

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