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Old February 23, 2013, 12:21 PM   #1
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C.0.A.L variations

I have a rcbs rockchuck press and dies and am noticing some inconsistencies with my C.O.A.L. I am getting a margin of error of plus or minus .0015. This leads to a difference of .003 at the extreme.
I am measuring from the ogive so it shouldn't be a variation in bullet tips.

What I am wondering is.. Is this normal and if not what are some possible causes? I am certain the die lock nut is tight.
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Old February 23, 2013, 12:25 PM   #2
Brian Pfleuger
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Normal and irrelevant.
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Old February 23, 2013, 04:00 PM   #3
Bart B.
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Bullet jacket copper stuff is not perfect in its metalurgy and dimensions. The ogive curve in the pointing die at the last stage of making a run of bullets will not be duplicated exactly for that reason. Plus, the lead core the jacket's formed around is different too, and it may push out or otherwise deform the bullet shape a few microinches.

A couple thousandths spread in the actual point on the loaded round's bullet ogive to the case head is not an issue and totally normal. They'll still shoot 1/2 MOA at 1000 yards if otherwise quite uniform and shot with good handloads in a proper rifle.

One can soft seat their bullets so they seat back a few thousandths by the rifling when chambered and eliminate that insignificant error. Besides, this better centers the bullet in the bore so it'll be less deformed in shape when fired.

Of the several dozen things required in making bullets shoot accurate, this one's about 3rd or 4th from the bottom.
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Old February 23, 2013, 08:08 PM   #4
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You're using too many decimal places. 3 digits is more than enough. Agreed; normal and insignificant.
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Old February 23, 2013, 08:23 PM   #5
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Brian nailed it!!
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Old February 24, 2013, 09:40 AM   #6
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Brian nailed it!!
He always does.
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Old February 24, 2013, 10:01 AM   #7
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Quote: Brian nailed it!!,,,, well sort of, Bart B. Triple nailed because he explained WHY, and Brian didn't bother with that.
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