Heckler & Koch ACR

The ACR, made by Heckler & Koch, of Germany, is derived from an earlier design, the G11.
The cartridge is caseless. This means that the bullet is packed in a solid compressed block of nitrocellulose. This cartidge is devired from the G11 : 4.7 mm. The Americans use the caliber designation 4.92 mm, but this is purely a question of measurement : 4.7 mm is the outside diameter of the bullet and 4.92 mm is the diameter between the grooves in the bore. An interesting feature is that the scope has two different positions : 1:1 for close range and 3:5:1 for range of up to 300 meters (984 ft).