KCI 30-Round M-1 Carbine Mags: Better Than the Original

The M-1 Carbine is one of the coolest and most versatile rifles ever built. Originally intended to replace the M1911 service pistol for World War II rear echelon troops, the Carbine quickly proved its worth for paratroopers, tank crews, officers, and even frontline infantrymen. It filled the nascent assault rifle role into the 1960s, while the US Army was still wedded to the outdated battle rifle concept. But as good as the M-1 Carbine was, and still is, its weak point was its magazines. The wartime industry never made durable, reliable mags. Fortunately, we have better choices now. One of those choices is the KCI 30-round M-1 Carbine mag.

KCI 30-round M-1 Carbine magazine
The KCI 30-round M-1 Carbine mag is better than the original GI mags. (Author’s Photo)

Magazine Woes

The wartime M-1 Carbine mags were so spotty that many soldiers just threw them away after using them once. When a Carbine mag was dropped for a reload, it usually stayed dropped. Soldiers simply picked up new mags by the bagful at supply dumps. The opportunity to do that speaks well of the US supply system, but the practice itself tells us how unreliable the mags were. Only a soldier with no other recourse habitually reused his mags.

The poor-quality Carbine mags represent US manufacturing priorities. Resources like steel were scarce. And, truthfully, aircraft, ships, tanks, artillery, and myriad other products were needed more than Carbine mags. It was cheaper to make more of the low-quality mags than to improve what was essentially a throwaway product anyhow.

Modern Day Mags

Nowadays, we don’t have those problems. Mags are still a consumable commodity to be sure, but civilian customers expect their mags to last far beyond a single use. M-1 Carbines aren’t as ubiquitous as AR-15s or even AKs, so there aren’t nearly as many choices. I currently own two Carbines and the best mags I’ve found are produced by KCI. Today, we’re looking at the 30-round version, simply because more is usually better. Let’s hit some basic specifications:

  • Weight: 0.3 lbs.
  • Compatible with M-1 and M-2 Carbines
  • Caliber: .30 Carbine
  • Body Material: Steel
  • Spring Material: High Carbon Steel Music Wire
  • Finish: Cation Electrodeposition Coating

I’ve been running KCI 30-round mags since I bought my first Carbine 18 months ago. I chose KCI because they had the best reviews. I’ve never had reason to look elsewhere.

Solid Construction

The KCI mags feel solid, despite their light weight. My first Carbine came with an old GI mag, and I can tell you that the KCIs are a definite upgrade. The spring is robust, and the anti-tilt follower is far better than the original. The spring is so strong that unloading the mags by hand requires some care. It’s not unusual to remove one round and have two or three more rounds pop out behind it. I can’t say for certain whether that affects feeding, but it doesn’t seem to. Either way, I’d rather the spring be a bit too strong than the other way around.

KCI 30-round M-1 Carbine magazine
The KCI mags have witness holes (circled) but they aren’t all that great. The bottom photos illustrate how the round is visible on one side but not the other. It’s no big deal to me. (Author’s Photos)

The KCI mags technically have witness holes on the sides, but you really have to look, and I never bother with them anyway. They only come into play once you’ve loaded 28 rounds, though a space along the magazine’s spine allows you to see the case heads if you pay attention. But again, I don’t care, and I don’t use them.

The electroplated finish is nice, and the mags eject fairly well, though their lightness sometimes means I have to help them along. The exterior finish, however, tends to wear off quickly where the mag engages the mag well. That doesn’t seem to affect performance one way or the other.

The feed lips can be a bit sharp and will tear your thumb up if you don’t load the magazines properly. I quickly learned to push them in from the top instead of the front.  And while the mag spring is strong, loading the KCI mags to capacity isn’t difficult.

You may notice that the 30-round mags are a bit loose in a standard M-1 Carbine. I’ve heard that installing an M-2 mag release fixes that. It doesn’t matter to me, so I haven’t bothered. But perhaps you might. The M-2 is the select-fire version developed near the end of World War II that saw widespread action in the Korean War and even into Vietnam.

Initial Issues

Given the Carbine magazines’ reputation, I was a bit skeptical of the KCI mags. At first, that skepticism seemed warranted. I had several failures to feed (FTF) and was generally disappointed. But I had read that most Carbines need their recoil spring replaced to run properly, so I decided to try that before condemning the mags.

 recoil spring
Replacing the M-1 Carbine’s recoil spring (circled) is easy and inexpensive. (Author’s Photos)

Carbine recoil springs are cheap. Wolff Springs has them for less than $10. Or you can buy an entire “Rifle Service Pak” containing replacements for every spring in the rifle, which was the option I chose. It still cost less than $25, including tax and shipping. I only replaced the recoil spring, but that fixed me right up. I still had a few FTFs, but just a few. I’ve learned that the KCI mags usually need to run three or four full loads to break in. They smooth out considerably after that and I rarely have problems. When I purchased my second Carbine, I immediately ordered another Rifle Service Pak and replaced the recoil spring. It’s super simple and takes about five minutes.

Running the KCI M-1 Carbine Mags

My Carbines are way too cool to sit in my safe or hang on the wall. I have a 1944 Carbine made by IBM and another made by Underwood Typewriter. In case you didn’t know, the US Government contracted weapons manufacturing to other industries to meet wartime demands, including those two companies. Others included the Rock-Ola Jukebox Company and Singer Sewing Machines. It was truly a total economic effort. My Carbines were made within two months of each other, but they have different sights and only one has a bayonet lug. The barrel bands are also different. That either speaks to how the various manufacturers were in different places as to the upgrades, or one (the IBM) was never upgraded after the war. Maybe it’s both. Either way, I like that they have small differences. Both do, however, have replacement stocks. That’s just the nature of the beast and is not uncommon.

Shooting the M-1 Carbine
The M-1 Carbine is a blast. This 1944 Underwood Typewriter model runs great with KCI mags. (Author’s Photo)

Being a history nerd as well as a gun enthusiast, my Carbines are in my training rotation. They don’t get the same work as my AR-15s or my AK-103, but I take them out and run them once in a while. I run the same drills as I do with my modern rifles. I have to say, it’s some serious fun. A handy 5 lb. rifle with very little recoil burns through those drills just fine.

But it wouldn’t be possible without reliable magazines. As I noted, I’m sometimes required to manually help them out, but you can train for that too. I do it with all my AK mags, so it’s not a huge deal. Like with my 30-round AR and AK mags, I rarely load the KCI Carbine mags all the way. The drills don’t require it and changing mags efficiently is a skill that must be practiced. But it’s nice to have that capacity if I want it. The Carbine would be a viable Zombie Apocalypse gun.

Honestly, the biggest issue to overcome was hitting the safety instead of the mag release and vice versa. It just takes practice. After running those drills for over a year, my KCI mags have hit the ground many times. But the steel construction has held up and they are all still running just fine. The only sign of wear is from the finish, as I mentioned.

A Good, Inexpensive Option for the M-1 Carbine

I use KCI M-1 Carbine mags exclusively because they work. They often require a break-in period, but that’s fine. Each one has run properly after that break-in point. And keep in mind that the Carbine’s recoil spring may be the cause of any issues you experience. Those things are old. The US hasn’t manufactured an M-1 Carbine since the 1940s, so your spring could well be almost 80 years old, even if the rifle was refurbished after the war. So, keep that in mind. I can’t speak to the newer reproduction Carbines because I have no experience with them.

KCI 30-round Magazine
I initially bought KCI M-1 Carbine mags because they had the best reviews. Now I run them because they work. (Author’s Photo)

The KCI mags are available, inexpensive, and they carry a lifetime warranty. I initially thought I’d use the GI mag that came with my IBM Carbine, but I haven’t. It just isn’t very good. I kept it because of what it is, but I don’t run it. There’s no reason to when I have better options. KCI gives me those options. If you’re looking for a solid M-1 Carbine mag, give KCI a try. It will likely make your experience that much better.

William "Bucky" Lawson is a self-described "typical Appalachian-American gun enthusiast". He is a military historian specializing in World War II and has written a few things, as he says, "here and there". A featured contributor for Strategy & Tactics, he likes dogs, range time, and a good cigar - preferably with an Old Fashioned that has an extra orange slice.

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