HB-9 updated text (PDF) - Corbin Bullet Swaging

The Myth of Equating BC with Accuracy
Another myth is that aerodynamic shape is synonymous with accuracy.
Years ago, I made some bullets that were just cylinders without any
ogive at all, and fired them from a benchrest rifle in .224 caliber into a
group that measured about 0.2 inches center to center. Then I fired another
group made with 6-caliber ogive spitzer bullets made exactly the
same way, with the same weight and diameter and the same materials.
These made almost exactly the same size group. The gun was at its limit
and the bullet shape had no effect on accuracy, except that the cylinders
landed a little lower on the target (more drag, so they dropped slightly
more).
In our work for various government agencies, Corbin made dies that
we called the “Ultra Low Drag” or “ULD” design, many years before the
popularity of the so-called “VLD” design of the late 1990’s. The two designs
are quite similar. In fact, nearly all low drag designs that are practical
utilize a long ogive and some kind of boattail. Ours used a nine-degree
rebated boattail, and a 14-caliber radius curve that was offset by 0.014
inches from the tangent (a secant ogive, in other words). There is nothing
magical about the numbers. There are dozens of variations which would
work approximately as well, better in some guns, worse in others.
There is a problem with promoting these buzzword designs: people
tend to believe that they solve all problems of accuracy, when in reality
they are very special designs made for certain kinds of loads, rifling twist
rates, and purposes. They are not always more accurate nor are they even
useful in some guns. Here are some of the problems with the very low
and ultra low drag designs (which means “high BC”, the ballistic coefficient):
To offer less air resistance, the bullet needs to be more streamlined,
which in turn makes it longer for the same weight, or lighter for the same
length as a conventional design. To keep the amount of shank in approximate
balance with the extra long nose (which would fill up with all the
available lead in a normal or light weight design and leave nothing for the
shank), these bullets are usually made in the heavier weights for the caliber.
This means that the long, heavy bullet has the center of balance shifted
toward the rear, so it wants to turn over more easily than the conventional
bullet, and thus requires a higher twist rate to stay nose first. If you have
a barrel with the appropriate faster twist, you may get a flatter shooting
bullet with equivalent accuracy to a normal design. Since the custom
swaged bullets are usually made with more care than mass produced bul-
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