The AR15.Com Ammo Oracle

History and Basic Design of .223 and 5.56 Ammunition.

Performance of .223 and 5.56 Ammunition.

Terminal Performance of .223 and 5.56 Ammunition.

.223 and 5.56 Ammunition Testing

Selection of .223 and 5.56 Ammunition.

Ammunition recommendations from the authors of the AR15.com Ammo-Oracle.

Purchase and Storage of .223 and 5.56 Ammunition.

Legal questions.

Miscellaneous .223, 5.56 and Other Ammunition Questions.

Ammo Oracle

Q. Do I want SS-109 or M855 then?

Between the two? Probably M855. As noted you never know for sure what your going to get with loads that are only marked SS-109. M855 shouldn't cause you any problems and is generally well liked by AR15 shooters. Don't worry if ammo is labeled as SS-109/M855. That should be M855 spec.

Note: M855 is effectively a implementation of the SS-109 interoperability standard (so all NATO members can shoot each other's ammo). The US, however, requires stricter standards in M855 and as a result, M855 manufacturers generally load their rounds to hit at least 3000 fps at 78 feet from the muzzle. The SS-109 specification had a lower 2985 fps requirement and British SS-109 rounds are slower still (2700-2800) to deal with the SA80 rifles.


Opinion: Some British SS-109 reportedly is underloaded (in order to permit proper operation in the L-85 Bullpup also called the SA-80 rifle) and therefore causes some short cycling in Bushmasters and Colts and isn't likely a good choice for emergency or critical use ammo.