1447744
EPR loadings: 7.62 mm
M80A1 at the front, with 5.56
mm M855A1 behind. (Orbital
ATK)
Date Posted: 07-06-2016
Author: Anthony G Williams, Derbyshire, UK
Publication: Jane's International Defence Review
The annual National Defense Industries Association (NDIA) Armament Systems Forum provided an insight into the
thinking of the US Armed Forces concerning future small-arms ammunition for the infantry squad.
Several major developments have taken place in the United States over
the past few years, including the army's enhanced performance rounds
(EPRs) in both NATO 5.56 mm and 7.62 mm calibres: the M855A1 and
M80A1 respectively.
These rounds are loaded with lead-free three-piece bullets consisting of a
hardened steel tip backed by a copper core, the two connected by a semi-
jacket that leaves the tip exposed. It is claimed that they can offer much
better penetration than the 5.56 mm M855/SS109 and 7.62 mm M80
NATO rounds they are replacing.
The US Marine Corps (USMC) has gone its own way with bullet
developments, introducing the 5.56 mm MK318 to a different design, but
US Congress in 2015 instructed the army and marines to consider
adopting the same standard 5.56 mm ball round, which seems likely to be
the EPR.
Saving weight remains a priority, particularly for a dismounted infantry.
This has prompted the development of lighter cartridge cases, which replace the usual brass with polymer except
for the base, which remains brass or steel as it has to be strong enough to withstand the violent extraction forces of
automatic firing. This can reduce the case weight by over 40%, but since the bullet and propellant weigh the same,
the overall saving in ammunition weight is around 20%.
Polymer cases bring further benefits; one being that the insulating properties of the material slows the transfer of
heat between the propellant and the gun chamber. Another is that the thickness of the material can easily be
adjusted to ensure that the propellant exactly fills the case, removing the air space (ullage), which is a source of
inconsistent burning and inaccuracy. The first such metal-reinforced polymer cartridge (the .50 calibre MK323) has
undergone extensive USMC testing, and others seem likely to follow.
This may only be an interim step, however, as significantly greater weight savings have been demonstrated by the
US Army's Lightweight Small Arms Technologies (LSAT) programme, now renamed Cased Telescoped Systems
(CT).
Hard target: US military outlines enhanced
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Weight concerns remain a priority and have driven the development of lighter cartridges
