5.7x40mm AVA

5.7x40mm EC
Type	Rifle
Place of origin	Entente Cordiale
Service history
In service	1978–present
Used by	Sieuxerr Sylva New Tyran EC
Wars	Various
Production history
Designer	Saint-Étienne Arms Manufacturer
Designed	1977
Manufacturer	MAS Manurhin Various other plants
Specifications
Case type	Rimless
Bullet diameter	5.7 millimetres (0.22 in)
Neck diameter	6.5 millimetres (0.26 in)
Shoulder diameter	8.3 millimetres (0.33 in)
Base diameter	9 millimetres (0.35 in)
Rim diameter	9 millimetres (0.35 in)
Rim thickness	1.5 millimetres (0.059 in)
Case length	40 millimetres (1.6 in)
Overall length	56.4 millimetres (2.22 in)
Rifling twist	1:12
Primer type	Small rifle
Ballistic performance
Bullet mass/type Velocity Energy 57 gr (4 g) Balle A FMJ 2,900 ft/s (880 m/s) 1,065 ft⋅lbf (1,444 J) 60 gr (4 g) Balle D AP 2,750 ft/s (840 m/s) 1,008 ft⋅lbf (1,367 J)
Test barrel length: 500 millimetres (20 in) Source(s): Arsenal Munitions Test Range

The 5.7x40mm EC is a rimless, bottlenecked, center-fired intermediate cartridge family. Designed in the mid-1970s, the 5.7mm EC and 7x51mm EC cartridges and their weapons would become standardized across the Entente and Entente-aligned nations by the 1980s.

History

Development of an intermediate cartridge began in the 1950s following capture and analysis of former-Ostlandic small arms, notably the StG-44 and the 7.92x33mm Kurz, and other, smaller production run experimental weapons. Another weapon that the Sieuxerrian Army showed great intrest in was the Hallian M1 Carbine and its .30 Carbine cartridge. Testing of these two rounds would lead to a number of other experimental rounds. Along with this, a series of new rifles and light machine guns were beginning development. However, development slowed as instead a replacement for the various rifle cartridges that had been in service during the PSW was prioritized. Using new understandings of ballistic theory, a 7mm round was developed and put into service, the 7x51mm EC cartridge.