6.91x55

From Epiverse

The 6.91x55mm cartridge is the standard cartridge for both the ADA and the British Army. It was developed alongside the program to design a service rifle for the ISS guardsmen.

History

The cartridge started out as a caseless round at 70mm long. It proved to be too bulky for the project, the length being so long that it was difficult to adapt to shortened carbine rifles. The caseless version was scrapped but the bullet was shortened considerably and adapted into a 55mm long cartridge. The 55mm cased round eventually won out as an international standard, though the caseless version was used in a handful of specialized firearms, and provided some of the initial research that sparked development of the SMX-16 Rex Anti-materiel cannon.

Ballistics

In practice it is best described as a compromise between assault and battle rifle ammunition, performing roughly in between them.

Firearms

Perhaps the most notable firearms to make use of the 6.91x55mm round are the BSA Sess, IDI Tehk-C65, and the JL G6. The New World was the only major power to never use the cartridge to any significant degree, preferring instead to stay with the established NATO assault and battle rifle cartridges (5.56x45mm and 7.62x51mm), with the ADA being the most prevalent user. The ASUN balanced its use as a logistical convenience against its own 7.62x39mm and 5.45x39mm rounds.