Lead pellets and ricochet
By B.B. Pelletier
"Do lead pellets bounce back?" is the gist of a question/comment I received yesterday on the Shooting BB guns post from June 28. This is a good question, because it relates to shooting safety.
Lead doesn't bounce straight back - but be cautious just the same
The article was about shooting steel BBs. Steel BBs bounce back with almost all their velocity. How fast they return depends on what they hit. The harder and more immovable the object, the faster they rebound. There is no place for the energy to go but back into the BB in the form of velocity in the opposite direction.
Lead, on the other hand, deforms easily, absorbing energy as it does. Think of it this way - a BB is like a baseball. When it contacts a hard, fast-moving bat, it goes in the opposite direction very fast. If, instead of the baseball you threw a lump of modeling clay, it would go splat on the bat and fly only a few feet. Lead is like the modeling clay.
When a pure lead pellet hits a hard, immovable surface face-on, its velocity converts to energy. The pellet starts deforming immediately. If velocity is low, the pellet flattens and falls to the ground. When there is too much velocity the lead cannot deform enough to absorb all the energy, so the pellet starts breaking off into smaller pieces. Some of those pieces fly away at high speed. When the impact is faster than 700 f.p.s., some of the smallest ones will absorb too much energy and become super-heated. If they get too hot, they flash to incandescence like a spark. Veteran airgunners who use steel bullet traps have seen sparks in their trap from time to time. These are fragments of lead flashing to incandescence.
Earlier, I said lead pellets do not bounce straight back - and they don't. But they do deflect, which is a grazing sort of "bounce" called a ricochet. The angle of deflection is dependent on the angle of impact, and it's not always easy to figure out. If a pellet strikes a hard immovable surface at exactly 90 degrees (that's straight on), it first smashes against the target, then parts break off and start deflecting on angles away from the impact. These deflection angles will not be 180 degrees, which is straight back at the shooter, but they will be greater than 90 degrees, which means they will come back in the same GENERAL direction as the initial shot. If the shooter is 10 feet away from a flat steel plate, someone 10 feet to either side of him might be hit by lead fragments splashing back.
If the fragments strike a second surface, the fun begins! They deflect off the second surface at a different angle and some of them COULD come back at the shooter. By this time, they've struck two surfaces and deformed twice, so a lot of velocity has been lost. If you are just 10 feet from the trap, you can still be hit pretty hard. A large lead fragment traveling at 400 f.p.s. (initially from a gun with a 900 f.p.s. muzzle velocity) will penetrate your skin and draw blood. I picked one out of my cheek just two months ago while doing some velocity testing.
Gonna end here, but there's probably more to say. Write me.