Magazine Material: Does Construction Matter?

When it comes to firearms design, the most important part to get right is the magazine. If there is going to be a failure in a modern firearm, whether it’s a rifle or a handgun, it is likely going to be in the magazine. Fortunately, the magazines available are, more often than not, reliable enough to bet your life on.

Loaded rifle magazine in hand with pistol in the background.

There are many options to choose from for most given firearms including steel, aluminum, and polymer magazines. Some magazines include a mix of materials, like steel bodies paired with polymer floor plates. Each type has its advantages and disadvantages, particularly when it comes to abuse and neglect. Follow along as we explore magazine material construction and why it matters.

Aluminum Magazines

Aluminum magazines generally consist of an aluminum body and base plate with the magazine spring and follower inside. The aluminum magazine baseplate will be dovetailed in place and held secure by a dimpled floorplate held under spring tension.

Few manufacturers use aluminum magazines with one notable exception being the USGI M16/AR-15. GI mags are cheap, plentiful, and reliable. There are no exterior plastic parts to crack or shatter and is lighter weight compared to steel-bodied alternatives. However, aluminum is a relatively soft metal. It won’t shatter, but it can dent. If the magazine body is dented, the magazine itself might not feed ammunition at all, with the follower stuck in its position lower in the magazine. Enough hard drops on the bottom of the magazine can warp the baseplate over time. While dented aluminum can generally be shaped back into place, it is not something that can be fixed on the spot on the firing line.

All-Steel Magazines

A Beretta Bobcat and a disassembled magazine on a table.
Firearms of a vintage design, like this Beretta 21A Bobcat, tend to use all-steel magazines.

All-steel magazines are a far more common choice among rifle and pistol manufacturers. Steel magazines are particularly common in older designs like the rimfire rifles, AR-15s, and the M1911 and Beretta platforms, and with good reason. These are, far and away, the most durable. Steel is about 2.5 times more dense than aluminum. That means any comparable stamped steel magazine will resist denting and deformation better than aluminum magazines. However, that density also means steel mags are going to be 2.5 times heavier! Given that steel is tougher to work with, it is more expensive than aluminum and polymer magazines. But sometimes the difference is marginal. For example, GunMag Warehouse offers Duramag steel and aluminum AR-15 30-round magazines. The premium for the steel magazine is $2.

Steel/Polymer Blends

Three Walther steel magazines on a table.
Steel magazines with polymer base plates are perhaps the most popular available today. The user gets a durable steel body and a base plate that is easy to customize.

Most newly manufactured polymer-framed handguns use magazines that I refer to as steel/polymer blends. Smith & Wesson, Sig Sauer, Ruger, Taurus, PSA, among others, use magazines of this kind. Usually, this consists of a steel magazine body and a polymer baseplate that is assembled in the same manner as aluminum and all-steel magazines.

The polymer baseplate serves both aesthetic and functional purposes. It blends in flush with the polymer of the grip frame to make for a single, hand-filling hold. The baseplate is oversized for the steel body, which helps the user grip the bottom of the magazine should it not fall free when it is ejected. The baseplate can also be removed and replaced with grip and magazine extensions that offer a fuller grip or extra ammunition—or both!

The only perceivable disadvantage of the type is the potential for the baseplate to break if a loaded magazine is dropped onto a hard surface. While hard to do, it is possible. One way around this is to distribute the polymer around the magazine, like what Glock does with their pistol magazines. Glock uses a steel inner tube to retain the spring, floorplate, and follower, but all inside an outer tube of polymer from the feed lips to the baseplate. Small wonder that shooters everywhere want every firearm to be compatible with Glock mags.

All-Polymer Magazines

Two MagPul PMags and two Walther magazines side by side.
Magpul PMags are completely reliable. But when stored in a ready condition, I tend to download them by a few rounds.

All polymer magazines, like aluminum magazines, are synonymous with the AR-15 platform. But polymer magazines have grown in popularity to include aftermarket Ruger 10/22, Glock, and pistol-caliber-carbine magazines like for the Sig Sauer MPX. Polymer magazines are, of course, not completely polymer. The magazine spring is still hardened spring steel, but all else can be polymer. Polymer magazines are cheaper to make and to buy than the alternatives, yet they are surprisingly durable, with a thicker baseplate to take the added stress of spring pressures and hard impacts. Polymer magazines are also the lightest of the bunch. If you are packing more than a firearm and spare ammunition, that can be a space saver.

The chief disadvantage of all-polymer magazines is the feed lips. When fully loaded, the spring pressure is allocated to both the baseplate and the feed lips at the top of the magazine. Unlike the baseplate, the feed lips must be thinner to allow the bolt or slide to pick up a new round with each shot. If left loaded for an extended period, the feed lips can become warped and feeding problems can occur. To get around this issue, some companies, like Magpul, make dust covers for their polymer magazines. When installed, the cover prevents ingress from getting into the ammunition. But it also takes spring pressure off the top of the feed lips. Alternatively, you can simply not load polymer magazines to capacity to prevent potential damage.

Options, Options, and More Options

In a typical range setting, when you go about selecting the right magazines for you, there is little need to be choosy. Aluminum, steel, and polymer magazines made by most companies tend to be very serviceable. For more serious work, construction does matter. Aluminum, steel, and polymer magazines give you more options, and each offers unique advantages when it comes to weight, durability, and cost.

The advantage of each kind is often going to be the disadvantage of the other. With steel, you gain durability for weight. With polymer, you gain small weight savings and a decrease in durability. All types of magazines will fail and operate in unusual ways. A bullet through a metal magazine can create burs that jam the follower and prevent feeding, while the same round through a polymer magazine might continue to function. But with any luck at all, this overview gives us an idea of where each stands and how to prioritize according to your needs.

Terril is an economic historian with a penchant for all things firearm related. Originally a pot hunter hailing from south Louisiana, he currently covers firearms and reloading topics in print and on his All Outdoors YouTube page. When he isn't delving into rimfire ballistics, pocket pistols, and colonial arms, Terril can be found perfecting his fire-starting techniques, photographing wildlife, and getting lost in the archives.

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