Curving Bullets

Episode #124

OAD: June 10, 2009

Myth: Sonic Boom Sound-Off

Can any sonic boom break any glass?

The Experts:

Captain Tyson Dunkelberger, Lieutenant Ben Walborn, Chad Swanson, Peter Carnicelli, and the rest of the US Navy’s Blue Angels team.

Memorable/Quotable Moments:

Adam’s expression during his flights.

Rob: And they call this “a job”.

The Action/Results:

Adam and Jamie agree to test two different sources of sonic booms for this one.  Everyone knows some jets can go supersonic, and the Blue Angels have agreed to help test this myth.  But some gunshots are also supersonic, and that’s also worth testing.

Before Adam can fly with the Blue Angels for the jet test, he needs to go on a qualifying subsonic flight.  Chad Swanson gives him a briefing on how to deal with the varying G forces he’ll be experiencing during the flight, and Lieutenant Walborn takes him up in Blue Angel #7, a FA-18 Hornet.  He nearly blacks out a couple times, and longtime viewers won’t be surprised to hear that he gets airsick, but neither of those interferes with Adam’s delight.  And, neither prevents him from being cleared to fly the supersonic mission.

But before the “jet test”, the guys want to see if the sonic boom caused by a supersonic bullet can break glass.  Jamie borrows a 50-caliber rifle and builds a support rig for it, while Adam mounts sheets of glass into frames.  They set up at the Chabot gun range.  The rifle is anchored and sighted in on a target.  On either side of the bullet’s projected path, they set up a corridor of window glass, glassware of varying sizes and shapes, and a glass wine bottle.  The first shot is made with the glass 7 inches (17.8 centimeters) away from the bullet’s path, and not only does none of the glass break, none of it even quivers in the high speed footage.  The glass is moved in to 2 inches (5 centimeters) away, with the same result.  Finally they try ½ inch (just under 1.3 centimeters) away, at which point the bullet hits the wooden frame holding the window glass.  But even then, the only breakage is caused by direct impact (from bullet or glass shrapnel), a lot of the glassware remains intact.

It’s time to test this myth with a supersonic jet, and for that Jamie and a ground crew head to the Marine Corps Air Station Yuma.  This is one of the few areas where the Blue Angels can legally fly supersonic over dry land.  They build a one-room house, complete with a glass window and glass chandelier.  Jamie also sets up a table full of assorted glasses and glass knickknacks, and parks a car nearby with its windows rolled up.

Meanwhile, Adam and Lt. Walborn take off for the supersonic flights.  Their first flight is at 8000 feet (2438 meters) altitude, and is less than impressive on the ground.  Jamie comments that he’s heard louder planes flying over his house.  They try again at 2000 feet (609 meters), but still no breakage.  The next flight, at 500 feet (152 meters), does no damage at the test site but does damage the skylight in the trailer at base camp.

Adam moves to the chase plane as Lt. Walborn takes #7 even lower, and adds a shallow dive to help focus the sonic boom on the test site.  After three back-to-back low-level booms, the door frame is broken, the window glass has fallen out of the frame, and the chandelier has fallen down … but none of the glass has broken.  They wrap up with five closely spaced booms at 200 feet (61 meters), the lowest they can legally go.  This time, they manage to break the window and knock the car’s rear view mirror loose.  However, all the glassware on the table survives.

Back in San Francisco, the guys agree that while it’s possible for sonic booms to break glass, it’s not the automatic result that the myth demands.  And that means the myth as stated is Busted.

Myth: Bend A Bullet

Are scenes in the movie “Wanted”, where assassins curve bullets around obstacles with a flick of the gun, possible?

Memorable/Quotable Moments:

Tory: I say we just let our cold-blooded assassin instincts take over!

Kari: OK, um, how ‘bout you hand me the gun, and then we’ll go with that plan?

The Action/Results:

The team wants to start by trying the “Wanted” arm swing themselves.  For safety reasons, they have to head out into rural northern California, where there’s no one to be hit by a stray shot.  Once there, they set up a target and the blast screen.  Each of them can easily hit the target with their handgun of choice firing directly at it.  Then a pig cutout (a reference to the movie clip they’re using) is placed in front of the target, and each tries again.  This time, bullets go everywhere except in the target.

Back at M7, Grant brings out the sword-swinging robot and turns it into a pistol-swinging robot.  The movie characters were said to have superhuman speed, and the robot can easily handle that.  Testing moves to the firing range at the South San Francisco Police Department.

While Grant sets up his robot, Kari and Tory construct five large frames covered with paper.  These go at 8 foot intervals down the firing range, to show if there’s any curve to the bullet’s path.  A test round is fired normally, and Kari aims a laser pointer through the hole in the first screen.  Grant and Tory see the laser beam shining through the hole in the last screen, showing that the bullet went in a straight line.

They first set the robot for human speed, and this matches their earlier result – the bullet goes straight through the paper screens.  Grant then cranks it up to double human speed.  Once again, the bullet goes straight.  Grant states that if there had been any deflection at all, he would have been willing to keep trying; but as it is there’s no point.  You cannot curve a bullet by swinging a gun around.

However, the assassins in the movie also had customized guns and ammunition.  Perhaps that could have affected the bullets’ trajectories?  Tory modifies several rounds.  Some of them, he cuts grooves in the bullet to make them nonaerodynamic.  On a second set, he drills a hole in the bullet and fills it with auto body filler to throw off the balance.  And finally, a third set is both nonaerodynamic and unbalanced – he drills holes in those bullets and leaves them unfilled.  Meanwhile, Kari modifies a gun barrel by smoothing out the rifling.  Rifling was added to firearms to make the bullet go straight, so a smooth barrel might give them the mythical curve.

In order to get usable high-speed camera footage, they run these tests with a stationary firing rig.  Once some control rounds fire normally, they load Tory’s altered rounds.  All of them travel straight through the paper screens.  When Kari’s smoothbore barrel is installed on the test gun, both high speed footage and the paper show that the rounds are tumbling – at least one goes through the paper backward.  However, they’re tumbling in a straight line.  There is no curve, and that means this myth is Busted.