Polygonal rifling

Polygonal rifling is a relatively new type of rifling wherein the traditional lands and grooves are replaced instead by 'hills and valleys' in a polygonal pattern, usually a hexagon. This has many advantages over the traditional form of rifling, in that it deforms the bullet less while also seals the gas slightly better, resulting in a slightly higher muzzle velocity in most cases. Because the bullet is less deformed, it is more accurate at long range, because it provides less surface area for the wind to push against. As a result of the fewer sharp edges pushing against the bullet, the barrel life is extended compared to a traditionally rifled barrel.

This type of rifling, however, has drawn criticism from various law enforcement agencies because the deformations traditional rifling leave on a bullet can be used to identify which gun fired the round. As a result, many of these agencies forbid the use of polygonal rifling so that shots fired by the officers may be identified as such.

Another disadvantage to polygonal rifling is that lead bullets fired through the barrel results in an accumulation of lead, a phenomenon known as 'leading', which can lead to poor accuracy or even barrel failure.

The most notable manufacturer to create barrels with polygonal rifling is GLOCK, though there are others who manufacture them as well, such as Kahr arms.