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How to guarantee the perfect bore ride diameter

Posted: Wed Sep 11, 2013 7:27 pm
by mtngun
This 30 caliber bullet dropped out of the mold 0.310" - 0.312". It's sort of a loverin design

I partially sized it nose-first in a taper die. The taper matches the taper in my rifle's throat.

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").

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".

Sooo..... the bullet is then sized nose-first in a 0.3085" push-thru die.

Now the bullet tapers from 0.302" at the nose to 0.3085" on the bottom 3 bands.

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-)