I invented the .11 UHV ("Ultra High Velocity") for a story. Its tiny tracer bullet would zoom out at UHV with no loss of V until it reached 100 yards, then it would stop and drop straight to the ground.
It deployed a tiny little parachute when the tracer material burned out.
Unfortunately, it got banned in New Jersey, Maryland, Ilinois, New York, California, and Hawaii, so the market evaporated and that was that.
For more detailed information, you can look up the patent or see the Wiki article.
Terry, 230RN