Originally Posted by
circuits
SS109 is an FN-Herstal designation for its "enhanced penetration" design 5.56mm bullet. When loaded to STANAG specs, it qualifies the loaded cartridge for the NATO cross and circle symbol on the headstamp and designation as "5.56 NATO".
When the SS109 bullet design is loaded to US military specs, it qualifies for the designation "M855" as well as "5.56 NATO".
Most of the "SS109" marketed commercial ammo does not even meet NATO, let alone M855 specs.
However, if loaded to M855 specs, the 62gr SS109 composite bullet has a mild steel penetrator embedded in a FMJ boat-tail lead bullet, and its acceptance criteria was penetration of both sides of an old steel pot type helmet at 600m when fired from the FN Minimi light machinegun (versions of which are in use with US Forces as the M249 SAW and Mk49, Mod something).
From the Ammo Oracle:
M855: Defined in MIL-C-63989
NATO specifications for M855 Ball require a 61.7 grain (q 1.5 grains) with a hardened steel penetrator at a velocity of 3,000 fps (q 40 fps) from a 20" barrel @ 78 feet from the muzzle. Typical velocity 15 feet from the M16A2's muzzle is 3,100 fps. Accuracy: maximum of approximately four MOA over the 100 to 600 yard range. Typical accuracy of average lots in an M16A2 is about 2+ MOA. This round must also penetrate a nominal 10 gauge SAE 1010 or 1020 steel test plate at a range of at least 570 meters (623 yards). The M193 round will penetrate this same plate reliably at 400 yards and about half the time at 500 yards.
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