Seating depth variance

Macmathews

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First off , I'm new to reloading.

Here is the problem, while seating bullets in almost any caliber.
The best I can do is about .008 thou varience and total spread is usually off by about .010 thou. I have noticed this while loading .204 ruger, .270 win and 7mm rem mag. Using a variety of bullets from Nosler BT to hornady vmax's. I'm sure of my measureing procedure, this seems to be consistant. Also if I seat the bullet twice, meaning seat it shallow , measure and add what's needed I can get them all within .001 or so.

Here's the tools used

Forster Co-ax
Forster Ultra micro seat and sizing dies

Steps are

#1 - Deprime only
#2 - stainless media tumble
#3 - lube and FL size
#4 - trim long brass to book spec
#5 - stainless media tumble
#6 - prime
#7 - powder
#8 - seat bullets

I have not started to load for proper COAL according to each rifle,and don't see the point if the best I can do is .010-.012


Thanks for any help
 

David_M

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Re: Seating depth variance

What measurement are you taking? Is it over all length (bullet tip to case head) or ogive length? If measuring overall length, the problem your facing is inconsistent bullet tips. Try measuring from bullet ogive and I bet your problems are solved. Good luck!

David M
 

Macmathews

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Re: Seating depth variance

I have been measuring overall length !
How do I measure from the ogive, would this not need a special tool ? , since there is nothing to "hook on"

Thanks for the help !

Kyle
 

Macmathews

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Re: Seating depth variance

I have been measuring overall length !
How do I measure from the ogive, would this not need a special tool ? , since there is nothing to "hook on"

Thanks for the help !

Kyle
 

justinbaker

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Re: Seating depth variance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kyle MacDonell</div><div class="ubbcode-body"> I have been measuring overall length !
How do I measure from the ogive, would this not need a special tool ? , since there is nothing to "hook on"

Thanks for the help !

Kyle
</div></div>
Yep you need a bullet comparator

Hornady makes one that works great for me.

About 20 bucks with 6 inserts

Check amazon or the big box hunting stores
 

EricCartmann

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Re: Seating depth variance

Lightly neck size 10 cases. Seat the bullet of each case at about 2.9". Then chamber each round, Measure OAL of each round after unchambering. Take an average. DONE and no special tools needed.
 

JSTARSZ

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  • Feb 6, 2008
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    Re: Seating depth variance

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: justinbaker</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kyle MacDonell</div><div class="ubbcode-body"> I have been measuring overall length !
    How do I measure from the ogive, would this not need a special tool ? , since there is nothing to "hook on"

    Thanks for the help !

    Kyle
    </div></div>
    Yep you need a bullet comparator

    Hornady makes one that works great for me.

    About 20 bucks with 6 inserts

    Check amazon or the big box hunting stores
    </div></div> you have to measure from the Ogive if you ever expect to be consistent with your numbers.
     

    David_M

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    Re: Seating depth variance

    Kyle,
    To do this right, you do need to use the bullet comparator like above mention hornady or equivalent. The ogive length is what matters most. When you press the bullet in short and then measure and press again to match overall length. You are then mismatching ogive length. The ogive length is what you want to match cause that determines the "jump" the bullet has until it meets the barrel. Hope that clears it up for you.

    David M
     

    Macmathews

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    Re: Seating depth variance

    All great advice and THANKS

    David, thought I was doing better and come to find out I was actually working against overall length !

    Thanks

    Kyle
     

    former naval person

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    Re: Seating depth variance

    While you are at it, try polishing the inside of the case necks with steel wool (0000) on a bore brush spun with a slow speed drill motor. I also paint a little graphite in alcohol inside the necks afterward. (Lockease) That tends to reduce the variance in seating force, thereby decreasing the OAL variance.
     

    QuiggyB

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    Re: Seating depth variance

    I find these bullet comparators work very well

    http://www.sinclairintl.com/.aspx/pid=33236/Product/Davidson-Seating-Depth-Checkers

    I don't see where inside the neck case prep would impact seating depth / cartridge oal. The bullet is pushed into place by a ram with a lot of mechanical advantage. It will impact neck tension which will affect pressure and velocity. So its important to do a good basic job of it and then how meticulous you need to be depends on what range you are shooting at. Mainly just brush out the necks and chamfer the necks when they are new or trimmed. If you have a need to get your velocities under 10fps of each other (say for 1000 yard competition) then take it up a notch and also get a lot more exact about how you measure your powder.
     

    QuiggyB

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    Re: Seating depth variance

    Also don't assume that two different types of bullets that measure the same length with a comparator will both be the same distance from the rifling in your rifle. The comparator doesnt necessarily touch the bullet in the same place the bullet will touch the rifling. Set up each new kind of bullet independently and then use the comparator to make more bullets exactly like it or to make adjustments to the bullet.

    I always start out by making a bullet that touches the lands, then getting the setting of my bullet seater to make that bullet and record the value.

    This is a good tool for measuring the maximum cartridge oal in your rifle. There is a video at that link that shows how to use it.

    http://www.sinclairintl.com/.aspx/pid=35491/Product/Sinclair-Bullet-Seating-Depth-Tool