7.62x39 vs 7.62x51

There's a lot of interest in short barrel 7.62x51 (308) guns out there in the community, but one question really should be asked:

At what barrel length does a 7.62x51 become worse than 7.62x39?

In this video we bring out a variety of guns and barrel lengths chambered in both cartridges and do *real science* to find out.

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