Physics of a 180 deg ricochet?

[1SOW]

In addition to all the emails showing ricochets, I experienced one that was literally a 180 degree ricochet. I fired at a paper target about 8 yards out. There was a piece of steel in the corner of the range about another 10 yards away. My 9mm FMJ went through the paper, hit the steel and came back as two pieces that went through the paper from the backside.

I'm not a physics major, but how can enough energy be generated to completely reverse --(180 degrees)-- a bullet after breaking up on a piece of steel?

 

[Oro]

how can enough energy be generated

The energy was generated when you pulled the trigger and burned the powder - no other energy was created. Work was done on the bullet to alter it's trajectory, but that's not the same as creating (or rather releasing/transforming) energy.

The bullet had enough kinetic energy (KE) for the whole flight. When it hit the steel, it transferred some of it's energy to the steel in terms of work energy (it moved it a little and likely dented it), but no new energy was generated.

The bullet came back at a substantially lower speed - reflecting the fact it lost energy in the collision with the steel. A rule in collsions like this is that "the angle of deflection equals the angle of incidence." That means if you shoot a cue-ball against the edge of pool table, it's going to move away at the same angle it struck the bank. So if the projectile came in at 180, it's going to leave at about 180.

Lastly, you should recall one of the mantras of gun safety is to know your backstop and that it is safe. This was not a safe place to shoot. If it was a commercial or public range, it is woefully bad, and if it was an impromptu place you chose to shoot, check the downrange field carefully.

 

[Double Naught Spy]

A rule in collsions like this is that "the angle of deflection equals the angle of incidence." That means if you shoot a cue-ball against the edge of pool table, it's going to move away at the same angle it struck the bank. So if the projectile came in at 180, it's going to leave at about 180.

Right, but this changes dramatically if you have shatter or splatter. Even slow moving .45 acp FMJ ball rounds can hit a target and come apart and when the come apart (due to becoming molten with contact [splatter] or breaking [shatter], much of the 'spary' is lateral and backwards, but not 180, although some may still come back on the 180 line. So you end up with a cone of incidence.

 

[Ridgerunner665]

In simple terms...it bounced back.

Steel flexes at tad...

 

[bonedust]

what you experienced would be called a 'splash', not a ricochet. its the same as throwing a water ballon against a wall....just alot faster.

 

[LightningMan]

As a cowboy action shooter, we shoot at steel plates all the time, and there are many factors involved with splatter or bounce back. Even though we only shoot lead bullets, I have seen bullets come back (in one piece) towards the firing line, doesn't happen often but it does happen. First and most importantly is target placement, targets should be perpendicular or directly in front of the shooter, and the target/steel plate should be angled down slightly to direct the splatter towards the ground. Targets themselves should be disguarded when they become concaved or convexed and dimpled/dented, this usually applies to poor quality steel as high quality steel like T2 will last much much longer when shooting lead only projectiles. LM
PS. I personally was timing a shooter once when he hit this target and the bullet came right back (I saw it coming) and hit me square in the chest. It had lost enough energy/velocity that it only thumped me like someone throwing a small rock at you. Made a small briuse on my chest. I would add that Cowboy action loads, require lead only bullets and velocities must not exceed 1000fps (pistol), 1400fps (rifle).

 

[jwr747]

it happens,I have a neat little scar on the left side of my belly,from a AK round that "bounced back" from a swinging plate about 35 yds.out. I now make sure any plates I shoot are angled away from me. jwr

 

[Dave B]

I had a 8mm fmj hit the edge of my shooting table after hitting a pretty beat up steel disc at 135yds. It was about the size of a mashed up 45 slug. It hit pretty hard too, about 8" from the muzzle. It would have been bad if it would have hit me in the face, or gone under the table top and got the family jewels.

 

[tipoc]

Once while at an outdoor range shooting .357 158 gr. hard cast lead SWCs at the 25 yard line. A fella was shooting two lanes over from me and walked up with a bullet in his hand and asked if I had shot this. I looked at it and saw it was mine. The round had gone through the target and into the dirt berm 10 yards behind the target. It had hit something hard in the earth and bounced back with enough force left to hit the fella in the shoulder two lanes down from me. Raised a welt on his shoulder. Put a slight dent on the round.

tipoc

 

[BCRider]

The owner of one range here said that if the energy from the round is able to dent the metal backstop or metal plate target into a bowl sort of shape then if another round comes in and catches the edge it can then slide around the curve and come back off the opposite side. If the dent is rounded enough the exit tangent can be right back at you. Well.... I added the bit about the tangent...

Otherwise I'd guess that it would be more a case of elasticity of the backstop material that "trampolines" the bullet fragments back at the shooter.

 

[1SOW]

Thanks for the thoughts guys.

Lead and copper/brass don't "bounce" significantly. I've often seen 9mm up to .45ACP hit steel poppers and fall to the ground in front of them. They are leaned forward a little

BCRider: The idea of hitting an indentation does make sense.. Part of the the original energy would still be available after it "diverted" around the dent. Probably the smother the dent the faster the bullet would be travelling. Mine came back in two or more pieces so it sure wasn't a smooth curve. Seems like a virtual 180 degree divert wouldn't happen too often though.

Steel plate for shooting has hardness standards that helps prevent those dents, but they eventually do get dinged up.

Thanks again

 

[W.E.G.]

Oh Willie!!!
http://www.youtube.com/watch?v=LvWv3Um5aRU

 

[ChemicalArts]

Oh Willie!!!
http://www.youtube.com/watch?v=LvWv3Um5aRU

My favorite part of that video is when the guy says, "Am I bleedin'?"

 

[GRIZ22]

the angle of deflection equals the angle of incidence." That means if you shoot a cue-ball against the edge of pool

This is true of light and may be for cue balls but there are factors that toss this out the window for bullets. A bullet will deform to some extent when it strikes whatever it hits. This deformation will affect the angle the bullet takes bouncing off what it hits. If it's a irregular surface this complicates figuring it out even more.

ps for example if you shoot a bullet at an angle into the ground the bullet will go down (deforming to some extent, bouncing off or deflected by stones) until it is easier for the bullet to go back up instead of continuing down. All of this is pretty unpredicatable and you can shoot a bullet into the ground and have it resurface (perhaps fairly well spent) a few inches or even a few feet from where it entered the ground.

 

[makarovnik]

You'll shoot your eye out kid.