Surefire’s 100-Round MAG5-100: The Highest Capacity AR-15 Magazine

Hunting with an AR-15 requires a low-capacity magazine of 5 or 10 rounds. Twenty-round magazines were issued to the first soldiers using M16s, and soon after the 30-round magazine was developed to give parity with the AK-47s encountered in the dense jungles of Vietnam. The 30 rounder became the standard detachable rifle magazine for all NATO countries in the early 1980s under STANAG 4179. For the past three decades, 30-round stick mags have been the norm for AR-15s used domestically and for M16s and M4 carbines used by our boys overseas. A few 40-round designs are offered but none has really caught on. Then there is the famous Beta C, a double-drum polymer behemoth holding a full 100 rounds and weighing 4.6 pounds when fully loaded. The Beta C hasn’t caught on with the military due to its need to be lubricated with graphite and fears that its complex design is too fragile for the rigors of combat.

The Surefire MAG5-100 is a true high capacity magazine
The Surefire MAG5-100 is a true high capacity magazine.

Surefire just released two new stick magazines to the public, with capacities of 60 and 100 rounds. I recently got my hands on the MAG5-100, and this thing is a true high-capacity magazine. A quadruple stack monster 1.5 inches wide and over a foot long, it still weighs only 3.3 pounds when fully loaded with 100 rounds of 5.56 ammo. It makes a big first impression. Inserted into an AR-15 carbine it looks almost comically enormous compared to a standard capacity 30 rounder.  Inside the aluminum body are three springs of different sizes which collapse inside each other like an old-fashioned telescope as the magazine is loaded. The largest, bottom spring is a super strong circular shaped monster that is the biggest and strongest magazine spring I’ve ever seen. An aluminum divider runs up the middle of the body, going through the middle of the springs and separating ammunition into two double stacks. The magazine actually has two followers. The “four-column follower” is the width of the bottom section of the magazine and stops at the point where the magazine necks down to one double-stack of rounds. At this point, the “two-column follower” rises up out of a hole in the middle of the four-column follower and finishes pushing the last few rounds up to the feed lips. Unlike the Beta C which uses plastic “dummy rounds” as followers, the two-column Surefire follower does activate the bolt hold-open device on the AR-15 and similar rifles. The feed lips are the stoutest I’ve ever seen on an AR-15 magazine, and they’d better be if they are going to keep from spreading apart with the force of those three huge springs pushing 100 rounds against them. Constructed using thick aluminum at the rear, the sides of the feed lips have square reinforcing ribs crimped into their shape. The front of the feeding area has a steel insert attached which features twin feeding ramps built into the magazine. Using this magazine in a modern “M4 cut” AR-15 upper receiver group will give the bullets three feed ramps leading to the chamber: one set built into the magazine itself, one set built into the upper receiver, and one set built into the barrel extension.

Surefire 5
California-based Surefire builds these in Nevada to avoid breaking CA law.

Despite being wide for a stick magazine, the Surefire MAG5-100 is much narrower than the double drum Beta C, so the shooter can use their regular grip on the rifle without having to bend an arm around the drum. On the other hand, the Surefire mag is so extremely tall that you can forget about ever going prone with it. This leads me to ponder what the magazine’s intended use is. Although the magazine is already in competition use by open-class 3-gun shooters like Jerry Miculek, I think its construction is stout enough to warrant serious consideration by private contractors and U.S. military special forces. For example, the Navy SEALs are known for their “break contact” drills, in which their small teams pour so much suppressing fire downrange that they often trick their foes into believing they are a much larger force. By the time the stunned enemy recovers from the initial barrage, the SEALs and their red hot barrels are long gone. The drill involves a lot of running mixed with dispensing large amounts of full auto hate towards the enemy, but going prone is never done while breaking contact, so the magazine’s length would be no disadvantage when used this way. Issuing a couple of 100-round Surefire magazines to each team member would give them emergency firepower on par with a belt-fed machine gun for the brief time needed to get away.

The MAG5-100 will cost around $160, so most of us won’t be buying one just for laughs and chuckles, but it’s still cheaper than the Beta C by around 50 bucks. Its smaller cousin the MAG5-60 runs $100. The price isn’t prohibitive to professional competitors or to those military organizations and private contractors who are always looking for a firepower boost. I commend the Surefire company for also releasing these magazines to the civilian market immediately instead of playing the coy “only elite Tier 1 operator guys can get these right now” marketing game that I’ve seen some other companies play in recent years. The Surefire high capacity magazine represents the cutting edge of ammunition feeding technology as it exists at this time, and I’m happy that it’s finally becoming available.

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Comments (5)

  1. I can only get 65 rounds in the magazine while loading. What is the secret of getting all 100 rounds inserted?

  2. You have a very good point, but if you are really shooting for your life, then I would rather have 100 rounds and not run out, because you won’t have time to reload. Needless to say, I would have a few other mags around just in case as an emergency standby, or better yet another gun with a 100 rd mag next to you ready to shoot!!

  3. It’s an interesting idea with perhaps some special applications. Though I think I’d rather have my ammunition spread across several mags in case something goes horribly wrong. Change mags vs. I’ve got 70 rounds below my problem… 😉

  4. We had two of the 60-round Surefire mags on hand for our latest machine gun shoot and one of them provided some nice mag dumps. The other magazine could not even be loaded, for some reason it was binding when it got to the bottom of the double column tower and engaged the main body followers. I’d have to talk to my buddy to see if he got a chance to tear the malfing mag down or if he just sent it back, I’d actually forgotten about it!

    I will say the other mag did perform flawlessly and loaded pretty easily from stripper clips and the various demo mags (60 and 100-round) that I saw at SHOT Media Day ran great.

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