The forward assist is critical in a rifle of the AR-15 design. Otherwise you cannot recover from some failure modes without taking the rifle apart. The rate o

The forward assist is critical in a rifle of the AR-15 design. Otherwise you cannot recover from some failure modes without taking the rifle apart. The rate of twist varies to stabilize whatever round is most commonly used. 1-7 and 1-9 are commonly used today due to bullet weight. Powder was an issue in the original issue Vietnam era M16.