Big Bore Cartridges for AR-10s & AR-15s

By Dean Roxby

Do you love big bore rifles? Somebody must like them, based on the variety of large caliber cartridges introduced in the last decade or so.

Years ago, the AR-15/M16 rifle was spoken of rather poorly by some, due to the small cartridge and “tiny” bullet. Now with caliber choices up to .50 inch, those complaints are rarely heard.

The real beauty of the AR family of rifles is their modularity. It is extremely easy to change virtually every piece of your rifle, if you so desire. This allows for all manner of customization. In particular, a change of cartridge is accomplished by a simple swap of the upper receiver/barrel assembly and perhaps a bolt and magazine swap. This applies to both the massively popular AR-15 platform and the AR-10 as well.

The trend of big bore AR cartridges is something that has intrigued me for some time now. Let’s take a look at what is out there. Please keep in mind that this article is merely an introduction and not meant to be a contest to determine “the best.” Attempting to do so would be an instant failure, as various rounds have different intentions. For example, the Am-Tac 416 Hushpuppy was meant for suppressed use, while the mighty .500 Auto Max is for hunting large, tough animals. It would not be reasonable to expect the Hushpuppy to match the Auto Max in power. To answer which is “Best,” we would need to clarify “Best at What?”

If you buy a complete rifle, it should be set up and ready to run—Well, hopefully. Buying an upper for your existing lower is certainly doable. After all, that is the genius behind the AR system. You may want to change the buttstock to one beefy enough to handle the recoil. Collapsible stocks are best avoided.

If you want to do your own start-to-finish build, you will HAVE to open up the ejection port for most if not all of these rounds to allow the fired case to be ejected cleanly.

The good news about magazines is that...

This article first appeared in Small Arms Review V22N8 (October 2018)
and was posted online on August 24, 2018


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