Book Review: Their Arrows Will Darken the Sun: Evolution and Science of Ballistics

By on August 4, 2013

Their Arrows will Darken the sun

I picked up the book Their Arrows Will Darken the Sun after hearing the author on Tom Gresham’s Gun Talk.  I’m kind of a ballistics geek and really enjoy the science behind how the bullet goes down range.  So when I heard about a new book by an expert on the subject, I just had to read it.

If you aren’t really into ballistics, you won’t like this book.  Ballistics can be really dry especially when you start introducing the mathematical formulas that can tell us what will happen as the gun goes off.  This book was even dry for me, and I love this stuff.

The book is broken down into four areas; BANG!, WHIZZ! THUD! and Technical Notes.  The first three represent the three common areas of ballistics, internal, external, and terminal.  The Technical Notes where on the engineer/physicist level and something I didn’t even get into, and here’s why.

The book started way in the past with thrown weapons and then catapults and into the 21st century.  It was a great start at history but the book kept going back to the beginning time and time again.  It was really too far in depth in most parts.

It was great to learn that a bullet’s shape got it’s origins with a javelin, but I didn’t need an entire page to compare how a javelin balances in the center and bullet is different because it’s balance point is to the rear of center.  The next page explained that this effects the trajectory of a bullet.

The most interesting part of the entire book was less then a page.  In it the author made a great argument that there should be a forth part of ballistics, the point the bullet leaves the barrel.  At first I thought that was just external ballistics and who cares?  But after he explained it, it makes sense.  There is something else going on there that’s different then any other time in a bullet’s life.

At the point the bullet is leaving the barrel there is a seal the bullet makes with the barrel preventing gases from going by.  Those gasses are the propellant burning and pushing the bullet down the barrel.  Right as the bullet leaves the barrel the burning propellant escapes around the bullet and accelerates past the bullet creating a vortex or vacuum the bullet has to push through before beginning what we think of it’s normal flight through the air.  The author wasn’t really sure what was going on right there and said more study is needed.  I think he is right, now that we can watch super slow motion cameras you can see this happening.  It would be cool to learn what is going on with the atmosphere and the bullet as those propellants blow by and create space in front of the bullet.

The other interesting thing in the book (and was a little bit above what I can understand) is what happens as the bullet goes supersonic.  Before the sonic boom the drag on the bullet is from the air pushing on the front of the bullet like a plane wing pushing air out of the way, or making the air speed up and move around the bullet.  When the bullet goes supersonic the drag is no longer in the front but is more a suction on the back of the bullet.  As bullet design continues to move forward we should see some more shapes that will be able to make our rifles even more accurate as designers change the shape to work with this new information.  The shape of the bullet needs to be different to be as stable as possible when the bullet is supersonic versus when it is subsonic.  The subsonic time includes when the bullet is accelerating down the barrel, the blow buy period as the bullet leaves the barrel, and a little time until the bullet actually creates the sonic boom.  I’ve tested distances with a suppressed 9mm and it takes a 9mm bullet about 5 yards before it creates the sonic boom.  The subsonic time of the bullet also is when the bullet slows down at longer ranges and is no longer going faster then the speed of sound.

Other then those two things, the book was kind of dry and boring.  It was written by a physicist and written on that level.  I never felt like I needed a degree to understand what was being said, but it really is the geekiest book on the subject out there.  If you are really into the how and why the bullet travels in flight and like the mathematical formulas you’ll like this book.  If you don’t want to know the mathematical formulas past mass times speed equals force, then you could probably skip this book.  If that sounds interesting, I read it on Kindle here.

Stay Safe,

Ben

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