This is a classic, and I'm actually embarrassed not to be remembering the name. It's a Cold War era (probably late 1950s to 1960s) story and set in a future where the Cold War has continued into space.
The setting is a U.S. lunar base where, in the aftermath of a battle between U.S. and Soviet soldiers, there is a cloud of bullets in (very) low lunar orbit. (Note this likely fixes the latest date for the story in the mid-1960s, since it was discovered before the Apollo missions that the lunar gravity field was lumpy enough to make most low lunar orbits unstable.) As a result the U.S. base (and presumably the Soviet one as well) are subject to repeated, periodic bombardment by the many bullets fired in the battle that didn't immediately hit anything.
It's possible there are actually 2 clouds, since the U.S. soldiers and the Soviets would have been firing in opposite directions.