How to guarantee the perfect bore ride diameter

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mtngun
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How to guarantee the perfect bore ride diameter

Postby mtngun » Wed Sep 11, 2013 7:27 pm

This 30 caliber bullet dropped out of the mold 0.310" - 0.312". It's sort of a loverin design
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I partially sized it nose-first in a taper die. The taper matches the taper in my rifle's throat.
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When it comes out of the taper die, the front band is 0.3025" (and the nose just ahead of the front band is 0.3020").
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The bottom half of the bullet did not get sized in the taper die. It's still 0.312", and I want it to be 0.3085".
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Sooo..... the bullet is then sized nose-first in a 0.3085" push-thru die.
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Now the bullet tapers from 0.302" at the nose to 0.3085" on the bottom 3 bands.
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As long as the taper die matches the rifle's throat, the bullet is guaranteed to be a glove fit in the throat. The sizing/seating depth can be tweaked by adjusting how deeply the bullet is pushed into the taper die.

Note that even though the nominal as-cast diameter was 0.312", a few of the bullets in this batch had heat shrink on the bottom bands and would not clean up in the 0.3085" die. They were set aside to be re-melted. Point being, it's common for as-cast diameters to vary. Casting is not a precision process, IMHO. The only 100% reliable way to guarantee a certain diameter is to cast a little oversize and then size the bullet.

Yes, it takes time to do this sort of sizing, but these are not casual plinking bullets, they are "serious" target bullets. ;) I have other guns and loads for casual plinking.

Using these dies, the same bullet can be either a 1) full diameter Loverin, 2) a tapered Pope-style bullet, or 3) a bore riding nose, depending on how I choose to size the bullet. 8-)

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