Multi-Caliber AR Mag

One of the weakest links in the reliability of the Stoner system is the magazine. Modern synthetic mags have greatly improved the situation, but things still get weird when you try and make an AR feed rounds other than 5.56mm. This year at SHOT Show I saw what one company thinks might be a solution for feeding different cartridges in the form of a multi-caliber magazine. The UNIMAG is RZE’s first production-ready firearm component and it claims to provide greater flexibility in ammo choice for gun owners and enthusiasts.

It’s compatible with AR-15s and other rifles that use a STANAG magazine, and is reportedly proven reliable and functional with at least six different types of ammunition. The secret is a two-piece, self-leveling follower that maintains stability while accommodating the changing shape and taper of different cartridges, and a self-adjusting magazine shell that adjusts to various cartridge diameters. Compatible cartridges include .223-Rem. and all of the cartridges based on that case (5.56mm, .300 BLK, .204 Ruger), 5.45×39, 6.8 SPC, 7.62×39, 6.5 Grendel and .458 SOCOM.


Scott Mayer

“Shooting Guns & Having Fun”



Scott Mayer

Scott Mayer

Writer at John1911
Mayer began his outdoor industry career in 1993 on the NRA Technical Staff where he became American Rifleman magazine first Shooting Editor. Mayer left NRA and entered the business end of publishing in 2003 as Advertising Account Executive for Safari Club International SAFARI Magazine and Safari Times newspaper. In 2006, Mayer was named Publisher of Shooting Times magazine where he was also tasked with launching and leading Personal Defense TV, the first television show of its kind.

In 2008, Mayer returned to the editorial side of publishing, this time in the digital field, as Editorial Director for Guns & Ammo, Shooting Times, Handguns and Rifleshooter online magazines. After a brief stint in 2011 as the Digital Media Director for an ABC TV affiliate, Mayer returned to the outdoors industry and Safari Club International where he is currently Assistant Publisher and Multi-Media Communications Editor.
Scott Mayer

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  • Isa Akhbar

    Off-label success! RZE doesn’t yet list the .450 Bushmaster for their Unimag, but it works:

    Well, we seem to have a new, functioning alternative mag for the 450b! Ran it through my Remmy R-15 with the Max-1 camo dip. Tight fit in the mag well, but not excessively so…I think the drag on the mag was due to the camo dip overlap up into the mag well on my particular rifle. If I cleaned the paint out of there, I think the drag on the mag (hey, that rhymes!) would go way down, but I’m pretty sure this mag would still be somewhat snug fitting. That’s just a minor complaint I have with my rifle, however.

    Full and partial mags functioned just fine, no observed problems…didn’t fire a large number of rounds, because everything seemed to work as advertised.
    Bolt hold-open worked fine.
    Top round position looked just right for the 450b, with the tip slightly “nose up” when held in the mag lips.
    Manufacturer recommends loading the mag carefully, so that the rounds double stack correctly and the top round is centered in the mag lips. Did that, and it worked fine. Whooda thunkit?
    I noticed while initially hand-cycling some rounds out of the mag that the mag lips were scratching the brass, so I smoothed them over with a 600-grit sanding stick and some metal polish on a Dremel wheel…problem solved.
    Finish, construction and overall quality seem top-drawer.

    Summary of my experience with the RZE Unimag: Quality product that works well with the 450 Bushmaster!