If worst comes to worst and you ever have to pick up your trusty M4 clone and go to protecting hearth and home, which carbine cartridge is most likely to save your life?

While this debate has raged through the decades, flaring with every significant improvement and/or change in firearms design and ricocheting off of every military contract and police department purchase—the subject has grown even more complex of late, due to the introduction of dedicated M4/AR-15 cartridges such as the 6.8 SPC, 6.5 Grendel and .300 Blackout.

Yes, I know: Many deserving carbine cartridges such as the 7.62x39mm want in. And sure, some of them will leave size-14 combat boot-prints all over the cartridges just listed. But much as I deplore the necessity, let’s confine this discussion to rounds in one arena: those appropriate for the M4/AR-15 family. Otherwise this article would turn into a book.

Trouble is, each popular carbine cartridge has significant strengths, especially in certain areas. What will work best really depends on you and your shooting abilities, your environment and lifestyle, and the probable demands those unique elements will place on your carbine.

Here’s a close look at the strengths and weaknesses of a handful of the best AR-15 cartridges available on today’s market. Only you can decide which is best, so be sure to vote for your favorite.

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