Home Forums Hunting & Shooting Ask The Gunwriters Impact velocity and bullet expansion

Here are graphical summaries of some of the data in the great penetration experiment.





The first chart is penetration vs. impact speed for a few common types of bullet. The second is the average of Speer, Sierra, and Hornady. Averaging reduces the random noise, and does a better job of showing the underlying trend.

The lessons of the graphs are:

1. Below a critical speed, the bullet fails to open. That gets you a very long skinny wound channel.

2. Above another critical speed, the bullet opens too much, too fast and either gives you a short fat wound channel, or, more likely, breaks up and gives significantly reduced penetration.

3. Between these two critical speeds, penetration is pretty constant. It doesn't matter much what the impact speed of the bullet is, as long as it is in that range.

4. For standard cup and core bullets, the critical range is about 2100-2800 FPS.

5. Not fully shown in the individual graph, the Barnes X and the Nosler Partition open reliably at around 1800 FPS and penetrate properly up to warp 9.8. They also produce deeper penetration that cup and core bullets. IIRC, Hornady Spire points open around 1800 as well, but I could be mistaken.

Manufacturers will tell you the optimum impact speeds for their bullets.