The M2129 is a family of standard issue battle rifles of the USSEC armed forces.
The M2129 utilizes the SCAR bolt in early models, and the Kriss Super V combined with the SCAR in later models. The most compact models use four foot barrels, while the sniper and support variants feature five foot barrels. All variants of M2129 are issued with SMART systems.
The M2129 is a bullpup battle rifle that resembles a combination of the Tavor Assault Rifle: 21st Century and FN F2000. It fires 16.5x60 USE type bolt ammunition. Several sniper rifles using the 2129 design fire larger rounds.
There are over a dozen variants of the M2129, many of them upgraded and updated models issued to specialized troops.
The only model that is not a rifle is in the M2129L automatic shotgun, or "Flooder", which gave rise to the name of the Flood-Fire Wars.