When out prairie dog hunting I'll come across a "mag dump" of 5 5 6 brass and gather it up and most of the time it's crimped. That brass gets donated to the local sheriff's department for them to get reloaded for training ammo as I don't mess with crimped primers.
AFAIK, the NATO STANAG (standardization agreement for ammunition among the NATO allies) calls for crimped primers. Military crimping of primers has been done since the 1920s to stop primers from popping out and getting jamming the works of machine guns. More recently, some commercial ammunition has started to have crimped primers, too, particularly 223 Rem.
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