I just had a look at some of my .458" bullet remains that I tested some 20 years ago.

All Hornady 500gr./.341SD RN SP fired from .460Wea at 2620fps. into a test media 20, 50, 100, 150, 200 yards away.

Impact velocity was not measured but to put the figures into the Pejsa ballistic program it would be 2555, 2470, 2320, 2180, 2040 fps.

At that time I didn't care about anything else but the bullet retained weight and shape.

At 20y/2555fps the bullet disintegrated including the copper jacket into many small pieces

All the other bullets kept their jackets and surprisingly mushroomed to the "same" diameter which was .750"-800" the only things that changed was the weight and the length of the remnants.

(242, 339, 416, 452gr.)

At 50y/2470fps the bullet mushroomed into .800"/.470"long and the jacket and the core remained together and retained 242gr.

Now the interesting bit here is the change of the SD. If the bullet wouldn't expand and kept the original .458" diameter the SD would be 0.164.

The remaining bullet frontal diameter of .800" and the remaining weight of 242gr. has changed the SD for the corresponding bullet diameter from .164 to .0540.

SD .054 means 79 grains bullet in its original .458" diameter

SD .054 means 98 grains bullet in .510" diameter

and/or 146 grains bullet in .622" diameter

SD .054 means 36 grain bullet in .300 cal.,

Maybe now we can better understand why expanding bullets have limited penetration.

Where penetration is concern the SMALL FRONTAL SECTIONAL AREA AND THE HIGH SECTIONAL DENSITY IS THE KING.

In penetration velocity plays a role, but velocity alone comes a secondary.

Pyzda

Interesting thoughts, I could follow the hypothetical math behind that.

Tyler

Well done, the theory of changing SD is actually a real life action of physics.

When the bullet diameter increases (expands on/in the target) the SD decreases accordingly as there is a change between diameter/weight ratio.

Pyzda