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Posted On: 6/21/2023
By: Simon
A: Thanks for reaching out Simon! You raise an interesting question. 308 Win and 7.62x51 cartridges share virtually identical exterior dimensions – so much so that a rifle chambered for either can safely chamber and fire both. The 7.62x51 NATO is actually loaded to a slightly lower chamber pressure than the commercial 308 Win. As such, a 308 rifle is more than hearty enough to safely accommodate the 7.62x51's lesser chamber pressure. But the difference in pressure is so minute that SAAMI does not consider it unsafe to fire 308 Win in a 7.62x51 firearm! Do bear in mind that some semi-automatic rifles may be fine-tuned for one cartridge's chamber pressure, but the general consensus is that treating the two rounds interchangeably. From Wikipedia: "Even though the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) does not consider it unsafe to fire the commercial .308 Winchester rounds in weapons chambered for the military 7.62×51mm NATO round, there is significant discussion about compatible chambers and muzzle pressures between the two cartridges based on powder loads, chamber dimensions and wall thicknesses in the web area of the military compared to commercial cartridge cases. As the chambers may differ accordingly the head space gauges used for the two chamberings differ."
