Game Changer: Shield Arms Glock 43x/48 Magazine Hold More Rounds

Photos: Durka Durka Photo        

Empty and loaded Shield S15 mags.

In the Summer of 2019, Shield Arms announced a new magazine for the Glock 43x and 48. By itself, this information did not appear to be newsworthy. However, if you looked deeper at the announcement, you knew something potentially big was coming. The mag in question, the S15, was not another standard aftermarket replacement mag. There were several key differences.

First, the S15 mag was made of steel. Second, instead of the 10 rounds that a factory 43x/48 mag holds, the S15 would hold 15 rounds — and it had the same overall height as the factory mag. To many people that seemed impossible. They thought the only way to stuff 15 rounds in the space of a 10 round mag is with sorcery.

Shield S15 mag left, factory G48 mag right.
Factory G48 mag left, Shield S15 mag right.

The truth is a bit simpler. All Glock mags are made of polymer molded around a metal shell. This makes the walls thick. That thickness limits the factory 43x/48 mags to a single stack of ammo inside. (Yes, I know there is a small stagger but it is closer to single stack than double stack).

Shield Arms basically looked at that and started experimenting with a thin-walled steel mag that allowed the ammo to be double stacked inside (two columns of ammo).

I spoke with Seth Berglee, one of the founders of Shield Arms.

“The Sig P365 had come out, and we were looking at the Glock 43 and we realized there was room to work within there,” Seth said. “We originally started with a G43 magazine, and when the G43x came out we switched to make that the primary project.”

With Glocks, you always want plastic on plastic and metal on metal. That’s also an easy way to remember which way the extractor depressor plunger and spring-loaded bearing go in the gun. The metal of the plunger goes against the metal of the extractor and the plastic of the bearing goes against the plastic of the slide cover plate.

So what about the factory plastic mag catch? Metal mags will tear up a plastic mag catch and a metal mag catch will tear up the notch on plastic mags. Well, Shield has a fix for this too. When you order your S15 mags you can also get a metal mag release. If you plan to run these mags I strongly recommend getting the mag catch too.

I ordered two S15 mags and the mag catch from Shield Arms and I had the parts in my hand in just a few days. I was skeptical the mags would even work at all, but the only way to find out was the try them. So as soon as my package arrived, I ripped open the plastic bag, yanked out the mag, and grabbed a handful of 9×19 ammo to load it. 

The first 10 rounds went fairly easily, like a factory mag. The 11th was much tighter and by 14 I was done. I could not get the 15th round in. I even tried an old trick where you put the factory mag loader on top of the mag, then slam it on a hard surface to get that last round in. I broke the peg off of two factory mag loading tools. Frustrated I decided to leave the mags loaded with 14 rounds for a couple of days. After letting the mags sit, I unloaded them and tried again. The first 14 rounds went in a little easier and I shouted with glee as I finally got that 15th round in. Make no mistake, these are the hardest mags to load to capacity I have used in 30+ years of shooting. So if you get an S15 mag, don’t get discouraged right away, be patient, and have strong thumbs. The first 10 or so times I loaded the mags they got a little easier and now they are still very stiff, stiffer than any factory Glock mag but it’s doable. If you have trouble, consider one of those fancy mag loading tools.

I mentioned this to Seth from Shield Arms. “We are working on spring vendors. There are not many shops that can do the quantity that we need” Seth said. “We tried a few designs, and we have gone with reliability over easy loading. We are looking at other coatings, spring designs, and geometry to make loading them easier sometime in the future.”

So the mags are hard to load; so what, I get 50% more rounds! At this point, I had not shot the mags yet and I was still skeptical that they would work given how much upward pressure the spring would be putting on the slide causing drag. It was time for live fire testing.

Glock 48 with factory magazine.
Glock 48 with Shield S15 magazine.

I hit the range with two S15 mags, my G48, and 500 rounds of my competition practice loads using Montana Gold 115gr JHPs. The MG 115 is a truncated cone shape and sometimes doesn’t feed as well as regular FMJ round nose bullets. I shot a variety of bill drills, plate racks, and other drills just to burn ammo and test the mags. In 500 rounds across two S15 mags, I had zero jams, failures to feed or other issues. The mags ran flawlessly. 500 rounds is not a lot, but it is enough for me to confidently carry my G48 with an S15 mag. Shield Arms has done way more testing than I did, however.

Back to Seth. “In our testing, we put many thousands of rounds through the mags before releasing them to the public. We have been through several iterations and design changes to get to where we are now. The first batch of mags we received we actually rejected. The finish has been a big deal with these mags. Having a really smooth finish allows them to feed and load a lot easier. If the finish is not mirror-like it makes a lot more tension. It does not seem to affect reliability much but it does make them harder to load. 

A very large Federal Law Enforcement Agency just finished some testing. We sent them two mags and they put about 5000 rounds between two mags with no issues. Some second parties have done some very high round count tests in addition to our own tests.”

The only issue I experienced was that the mags don’t really want to fall out of the gun, full or empty. This seems to be due to the variable tolerances of the mag well from gun to gun and the S15 mag being about 10 thousandths wider than the factory mag. 

Seth responded, “The one major battle that we have fought, is that Glock has changed the frame at least twice since the pistol was released. The silver slide guns have less polymer in the grip. Specifically around where the slide release is. Sometime between the silver and black slide guns they added material and built it up slightly. Some guns our mags sit a little lower or higher. It has been a challenge making sure our mags run with all guns.”

For a carry gun, I’ll take 15 rounds over 10 rounds every day, even if I might have to pull an empty mag out. Same for the mags being hard to load; I don’t care because I get 50% more bullets. I also don’t load carry mags very often, making it even less of an issue. Surprisingly, the S15 mag weighs a bit less than the factory mag when empty (see below).

Let’s look at the differences when comparing my G19C (with solid barrel) vs the G48. Ammunition used is Hornady Critical Duty 135gr +p.

G19 Empty, no mag 1lb 6oz
G48 Empty, no mag 1lb 3oz
G19 Empty Mag 1lb 8.6oz
G48 Empty S15 mag 1lb 5.1oz
G19 Full mag and chambered 2.0lb
G48 Full factory mag and chambered 1lb 10.2oz
G48 Full S15 mag and chambered 1lb 12.3oz
G19 Slide Width 1.004 inches
G48 Slide Width 0.861 inches
G48 Factory mag Empty 2.3oz
G48 S15 mag Empty 2.1oz

Ready to go, the G19 is only 3.7 ounces heavier and 0.143 inches wider. Those numbers by themselves seem insignificant, but the reality is the G48 with S15 mag feels much lighter in the hand and holster and much thinner on the hip. 

Glock 19 left, Glock 48 right.

S15 mags are a game-changer, period. I often carry a G19. The G48 is basically the same length and height except thinner and lighter, meaning it is easier to conceal and more comfortable to carry. I’ll keep my G19 for winter when it is easy and comfortable to carry 2 spare 17 or 20+ round mags, but when it warms up, which is most of the year here in Arizona, a G48 with an S15 mag will be my new go-to carry gun.

Shield has plans to release an ambidextrous version of the S15 mag and later an expanded capacity G43 mag.

For more information visit Shield Arms website.

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S15 magazine details. Photo courtesy of Shield Arms.
Magazine Comparison. Left to Right G48, S15, G19.
Magazine Comparison. Left to Right G48, S15, G19.
The red color visible through the witness hole is the follower. This shows how little room is left for the spring and follower at the bottom of the mag.
S15 loaded with 15 rounds of Hornady Critical Duty 135gr +p.
Glock 48 left, Glock 19 right.  Both guns feature Heinie Slantpro night sights.
Factory G48 mag left, Shield S15 mag right.
Empty and loaded Shield S15 mags.
Empty and loaded Shield S15 mags.
Empty and loaded Shield S15 mags.

About the author: Matt Kartozian is a current Hi-Point Grand Master and former professional competition shooter, and gunsmith. Matt now works as a photographer and writer and can often be found on the sidelines of professional sporting events and on racecourses around the world. You can follow Matt’s adventures on Instagram at and

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  • Scott September 21, 2020, 12:06 am

    In an update to an earlier post I have fired a over 300 rounds of various loads through three S15 magazines in the last few months without any problems. They seem just as well made as any Mec-Gar mag and are a bit easier to load (at least for me) than my P365XL 15 rounders. It is hard to say how they will hold up over time or how long they can be left loaded and still be reliable but so far I am very impressed. They make the 48 a really great carry option.

  • Jeb May 23, 2020, 12:59 pm

    I agree on the “game changer” description. My 16 round Glock 48 is now my edc.

  • Scooter May 19, 2020, 9:59 pm

    It really is a great design and product concept. I have tried a few of these magazines and can attest to the fact the mag will not consistently drop free. Also when using the slide stop lever to send the slide home to chamber a round I have encountered multiple failure to feeds(with various brands,weights,profiles). Hats off to Shield arms for the innovation in time they will produce a perfect magazine.

  • Ej harbet May 19, 2020, 8:57 pm

    I rented a g48 and it was the most accurate glock i ever shot. When mine gets to me and is proven with s15 mags my custom g19 becomes a spare. Ill probably be happy with 14rds in the primary and 19rds in the extended one! Oh theybdidnt mention that did they.yes virgil your spare s15 can have a factory extension. Makes for a nice house gun when you get home

  • DrThunder88 May 18, 2020, 3:07 pm

    “Game changer” is an overused cliche, but it does seem to fit the bill with these magazines. Getting what amounts to a full size pistol’s magazine capacity in trim packages like the 43x and 48 is outstanding. I’d like to see more models from Glock on the this form factor, and the S-15 magazines are the key to it.

    The only downside to the S-15s are that they don’t fit quite as snugly as factory mags in my kydex mag pouch.

  • Scott May 18, 2020, 11:29 am

    If these magazines are reliable to the point of betting ones life on them they are wonderful indeed. As both have available fifteen round magazines how about a comparison of the 48 to P365XL? The P365 series mags take considerable effort loading to capacity as well.

  • the-phil May 18, 2020, 9:33 am

    I bought a G48 just because of these mags and I don’t really like Glocks. The weight and width difference is dramatic and for a Glock the G48 feels great in the hand.

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