Q: I’ve found that the shellholder for my .30-06 won’t accept .308 cases. This is because the extractor groove of the .308 is much wider than that of the .30-06 family of cartridges, though the head diameter is the same. What is the reason for the marked difference at that point?
Norman Simpson
A: Although the .308 Winchester like the .30-06 is of military origin, a modern military cartridge must be designed with its use in automatic weapons as a major consideration. The extractor groove of the .30-06, while entirely adequate for use in turnbolt rifles in which most military cartridges were used at the beginning of the 20th century, was found to impose a handicap in the design of some automatic weapons. The 7.62x51mm NATO was therefore designed with a wide extractor groove allowing extractors of dimensions suited for such weapons. The wide extractor groove is no drawback to its use in turnbolt rifles and might even prove to be an advantage. The .308 Winchester is the sporting version of that cartridge. I’ve also found some shell holders that wouldn’t accept the .308.
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