AR companies have admitted to using the 5.56 chamber for guns marked as 5.56 and for those marked only as .223 Remington.
the SAAMi drawings for the official ".223 remington' chamber predate the use of fast twist barrels in .223 and as such are still set up for the original slow twist.
IF the 5.56 can ONLY use the long bullets because of that throat, and .223 Remington comes with those nice long heavy bullets, and companies use those bullets for testing..
How is there even a difference? kind of like debating the merits of "rifle" and "handgun" load data for .357 magnum or .44 magnum...
But I see no one wants to debate the CIP pressure standard versus American saami pressure limits.
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