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The Ultimate Reloading Manual
Wolfe Publishing Group
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The Ultimate Reloading Manual
hornady superperformance

Bullet Behavior

Author: Richard Mann / Wolfe Publishing Co.
Date: Dec 19 2008

When handloading bullets for hunting big game, it’s important you know how those bullets will behave inside big game animals and what that behavior means. While working on the book Rifle Bullets for the Hunter, I developed a way to classify bullets based not on their cost or construction but on what matters most: their terminal performance. This makes sense because a bullet’s ability to kill is determined by its terminal performance and its path of travel inside the animal. If two bullets provide identical terminal performance, they are the same as far as the handloading hunter is concerned.

These two expanded Swift Scirocco IIs
illustrate how different impact velocities make
bullets perform differently. The expanded
bullet on the far right impacted at 3,190 fps
and behaved as a balanced bullet. The
expanded bullet to its left impacted at 1,811
fps and behaved as a penetrator. 6

After testing hundreds of bullets in a variety of mediums, I found that penetration could be reliably predicted by the weight and expansion of the recovered bullet compared to its impact velocity. This may appear to be worthless information because if you can recover a bullet then you know how deep it penetrated. It’s important because it shows that terminal weight, expanded frontal diameter and impact velocity control penetration depth. It also shows that without consideration of terminal performance, an expanding bullet’s unfired diameter and weight – sectional density – give little indication of how that bullet will penetrate or how much tissue it will damage.

Bullets behave between two extremes: They either fragment or they do not expand at all. Most big game bullets fall in the middle. To better understand bullet behavior, it makes sense to break down expanding bullets – the bullets in the middle – into three additional classifications: maximum expanding, balanced and minimum expanding.

FRAGMENTING BULLETS

Any bullet that retains less than 30 percent of its unfired weight after penetration is a fragmenting bullet. As impact velocities drop, many bullets that behave as fragmenting bullets at, say, 100 yards may act like a maximum expanding bullet at 200 or 300 yards. Fragmenting bullets are best suited to varmints because of shallow penetration.

MAXIMUM EXPANDING BULLET

Most of the bullets hunters have been using for big game for many years behave like maximum expanding bullets. We’re talking about bullets like the Remington Core-Lokt and Winchester Power-Point. Maximum expanding bullets can retain as little as 35 percent of their weigh tor as much as 100 percent and expand from 1.0 to 2.5 times their original diameter, respectively. These bullets have developed a great reputation on big game because they create large wound cavities and typically penetrate deeply enough if they do not impact at too high a velocity.

Except when their petals break off during
penetration, Barnes Triple-Shocks almost
always behave as balanced bullets, expanding
to about two times their original diameter
and retaining 100 percent of their weight.

BALANCED BULLETS

Balanced bullets balance expansion and weight retention, allowing them to penetrate deeply and create wound cavities that destroy a lot of tissue. By building a wall between the front and rear core inside a bullet, John Nosler created the first balanced bullet with the Nosler Partition. There are other ways, however, to make a balanced bullet. The Swift Scirocco II is a perfect example of a bonded bullet that behaves as a balanced bullet. Likely, the most consistently balanced bullet made today is the Barnes Triple-Shock. (The E-Tip, Lapua Naturalis and newer Hornady GMX and Remington Premier Copper Solid are very similar.) These bullets typically retain near 100 percent of their weight and expand to about two times their original diameter, giving them a BBC rating of 50. This puts them square in the middle of the balanced category. Good balanced bullets behave as balanced bullets when impacting at high speeds and over a wide impact velocity range.



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