M27 link
The M27 link, formally Link, Cartridge, Metallic Belt, 5.56mm, M27 is a disintegrating metallic bullet link issued by the United States armed forces and designed for use in belt-fed firearms. It holds 5.56×45mm NATO ammunition. It was first developed for the Stoner belt-fed Machine Gun in Vietnam but was later resurrected and adapted for use with the FN Minimi LMG / M249 SAW.[1] It is a scaled-down version of the M13 link.[2]
Each link consists of a single piece of metal curved into two partial cylinders, into which adjacent rounds slide. Like the M13 link, the M27 link is a push-through design. Rounds are extracted by pushing forward out of the link. With the round freed, the link disintegrates (detaches from the belt) and is ejected. This is in contrast with older belt systems which were typically made of fabric and were fed straight through the weapon without disintegrating.
The links can be collected and reassembled by hand with fresh ammunition, but in practice this is not commonly done as it is labor-intensive, and the inexpensive links are considered disposable.