.308 vs 7.62×51 Ammunition My “Serious Purposes” Warning

By John Farnam

Opinion

Ft Collins, CO –-(Ammoland.com)- As most of us know, 5.56×45 is the “militarized” version of the civilian 223 Rem varmint cartridge, developed by Remington in 1957.

Military-rifle chamber dimensions for the 5.56×45 cartridge are more generous than the civilian 223 (SAAMI-spec), although both rounds will chamber and fire in NATO-spec military rifles.

SAAMI stands for “Sporting Arms and Ammunition Manufacturing Institute.” SAAMI was instituted in 1913 in order to establish and exchange consistent small-arms technical information between American factories producing military arms and ammunition.

Today, SAAMI continues to dictate chamber dimensions and pressure standards for all commercial calibers, and all gun and ammunition manufacturers dutifully comply.

Commercial rifles in 223 Rem caliber, intended for non-serious purposes, mostly come with SAAMI-spec chambers, which are tighter than NATO-spec chambers, as noted above.

As a general rule, when a barrel is stamped “223 Rem,” it has a SAAMI-spec chamber, and as noted above, it is intended only for non-serious purposes. Tight chambers boost accuracy but have no place on high-capacity, military rifles.

Conversely, when the barrel is stamped “5.56×45,” it has a looser NATO chamber, with adequate leade, or freebore (this is a short section of bore just ahead of …Read the Rest