The .300 Blackout is one of the more interesting calibers in recent years, officially approved by SAAMI in 2011, and born out of a need for a specialized close-combat round for special operations units, the .300 AAC Blackout has become one of the most popular chamberings for the AR-15 platform – and for a good reason.
Offering better ballistic performance and stopping power than the standard 9mm (the most popular subsonic SMG round) in subsonic AR setups, and you can run standard 5.56 magazines with any rifle chambered in .300 Blackout as the case dimensions are close enough to function in both.
In This Article
Comparison of the Best .300 Blackout Magazines
Below is my list of the best .300 BLK magazines for 2021. I list the best choices in terms of value, performance, design, and cost.
Click on the name to head to the product page, read reviews and check prices or skip ahead to the list of magazines.
What to Look for in a .300 BLK Mag
1. Identifiable differences
While running a common magazine is convenient (one of the central features of the .300 BLK is you don’t have to change anything on your 5.56 AR beyond the barrel), there’s additional safety in dedicated magazines, which help mitigate dangerous cross-loading issues (chambering and firing the wrong ammo, causing a catastrophic out of battery detonation).
To keep things as safe as possible, we recommend dedicated 300 Blackout magazines, and magazines that offer unique color, distinct follower, or identifiers to ensure it’s clear which magazine houses 5.56 and which contains .300 BLK. Having magazines for rifles chambered in .300 Blackout will mitigate cross-loading, provide additional safety measures, and give you another reason to add to your kit. What’s not to like?
2. Brand names
Additionally, some of our favorite manufacturers have crafted dedicated .300 BLK magazines. While these mags are, in many ways, identical to those 5.56mm variants, our recommendations will make it easier to tell them apart in your range bag, give you a sense of the best brands and features – all while keeping price point in mind. No need to head to the bargain bin for your BLK.
The Best .300 Blackout Magazines Reviewed
1. Magpul PMAG 30B GEN M3
The Magpul GEN M3 is a go-to magazine in any caliber and their .300 BLK mag is no different. Like its smaller-calibered brethren, the .300 BLK version retains all of the great Magpul GEN M3 features – like their crush-resistant polymer & aggressive front and rear texture. This generation’s impact and crush resistance, anti-slip and anti-tilt tech make them some of the most durable and best-designed magazines for rifles available.
These Pmags mitigate cross-loading by adding .300 BLK-specific features – like distinct rib design, rear texturing on the magazine body, and an easily-removable, slim floor plate. Additionally, they also have the GEN3 paint pen dot matrix, so you can denote .300 Blackout on the magazine itself.
2. D&H AR-15 20 Round 300 AAC Blackout Magazine
Instead of opting for an aggressive front texture or specific ribbing, D&H keeps cross-loading at bay with a simple approach: include a visual indicator of the caliber on the magazine from the factory.
These magazines from D&H offer a 20-round capacity and a bright red follower paired with a specially-calibrated spring which improves follower/spring tracking and feeds the heavy .300 Blackout rounds more effectively than a standard 5.56mm magazine.
They’re made out of high-quality, black anodized aluminum for years of service and a solid lock into any AR mag well. The inclusion of the caliber on the magazine from the factory is nice and certainly looks more consistent than a DIY job with a paint pen.
One thing to keep in mind with aluminum magazines, they’re durable but can bend and dent rather than break (like polymer magazines might). With that said, it’s always a good idea to inspect the feed lips on aluminum mags occasionally to ensure they’re still in shape, especially after considerable use or they’ve been dropped.
3. Hexmag HX40 Series 2
Most AR owners have a lot of black Pmags laying around — it’s not uncommon to have a dozen or more at hand. Grabbing another Pmag and painting it for .300 Blackout might not be the best choice.
Many shooters will dedicate specific types or brands of magazines to specific calibers. Breaking calibers out this way further prevents mix-ups and improves safety by making it easy to pair a specific caliber with the correct magazine.
Right in the same budget ballpark as the Pmag, these Hexmags have a hexagonal texture on the whole magazine, a red follower, and a matching red button on the bottom to view the floor plate.
These simple touches make you less likely to misidentify the magazine, making these more than worth looking into. Using different mags for each caliber (like Hexmags for .300 BLK and Pmags for 5.56mm) will prevent cross-loading and simplify your range day packing.
4. Magpul Pmag 20 Round M3
Another way to avoid cross-loading — again keeping the feel of the magazine in mind — is to change its shape, and this 20-rounder from Magpul has a shorter length than the 30 rounder, making it easy to distinguish.
The 20 rounder offers the same great Pmag features but measures in at a few inches shorter — so it’s smaller in-hand. Add some visual indicators like a specific caliber in the DOT matrix, and this gives you a great solution without breaking from Magpul products if they’re your thing.
5. Magpul M3 Windowed Pmag
Keeping with the theme of changing things visually, many shooters use windowed Pmags for specific calibers like the .300 Blackout. We all have black magazines lying around, so changing both the color and adding a clear window to inspect the remaining rounds will help avoid confusion and give you an even more useful magazine for .300 BLK rounds.
One potential downside is these are traditional 5.56mm Pmags (which include the “5.56×45” notation) so if you’re not going to use the color of the magazine itself and a differentiator it’s would be a good idea to use a paint pen to clearly demarcate the intended caliber.
Again, the idea is to give yourself as many visual and tactile indicators of the intended caliber on the magazine, and we think these do a very good job at that. The window itself is also handy for keeping track of remaining ammunition.
Why use a .300 Blackout Magazine?
- Differentiation. You can certainly use .300 BLK rounds in a 5.56mm magazine without issue, but commingling different cartridges in common magazines is just asking for pain. A dedicated .300 Blackout magazine gives you a chance to load your BLK in a specific magazine, which you can paint a bright color or use another visual indicator (such as a paint pen or different colored follower) so that you know which magazines are which.
- (Potential) Reliability Issues. Are we going to tell you that using .300 Blackout rounds in a standard 5.56 magazine is sowing future problems or going to create issues down the road? No. Are we proponents of using the right tool for the job whenever possible? Absolutely. The internal geometry of the 5.56 and .300 Blackout mags is indeed different, with 5.56 mags occasionally “pinching” and leading to a slower load. It’s a thing. Plus, magazines are cheap. There’s no reason not to have a set of make for your Blackout setup.
Important .300 Blackout Mag Features
- Magazine Material. Modern magazines all tend to use some kind of polymer, but there are both metal options available and a variety of polymers used in .300 BLK mags. For instance, Magpul touts the fact their mags are crushproof, while Lancer uses translucent, hybrid polymer/steel design that provides a visual indication of rounds on tap, but may be less durable than the Magpul approach.
- Feed Lips. Feed lips are the last mile of the magazine — they’re where the round is handed off to the bolt carrier in the chamber, which is a volatile environment. Magpul uses polymer feed lips, and are incredibly proven performers in any environment, but if you prefer steel feed lips you’ll want to look for Lancers or other brands that don’t put polymer in their lips.
.300 Blackout Magazine Pricing
Most magazines are cheap and plentiful, and the same is true with .300 Blackout mags. Quality options can be found for as little as $15 (or less with a decent sale) and you should have no fewer than 5 mags for every gun you own, so there’s really no excuse not to stack them deep. Usually, the pricier the stick, the more durable and versatile the materials, but a $15 magazine will get you a long way.
Don’t be fooled by gimmicky mags with strangely high price points: even the most proven .300 Blackout mag shouldn’t cost you much more than $20.
Types of .300 Blackout Magazines
Real talk time, kids: most AR magazines, regardless of caliber, are relatively similar — it’s the subtle differences that truly distinguish them from one another. A standard .300 Blackout magazine, for example, might consist of little more than a polymer mag with the correct internal geometry for the Blackout while a more Gucci mag (is that a thing?) might offer windows or translucent sides, steel feed lips, or simply more capacity.
What’s most important about a good .300 Blackout magazine is that it works well with your build and enables you to switch between common AR rounds safely and effectively.
How we selected these products
When reviewing guns or gear, we get our hands on as many products as possible, but there are times when certain products or categories are a real challenge — be it availability, cost, or simply a lack of resources — we can get stymied going hands-on with all the potential candidates. Plus, the magazine category is freaking huge, so rather than present a never-ending list of all the magazines that work with a .300 Blackout we selected those which we felt best represent the price points laid out above — giving you a solid representational list to serve as a jumping-off point for your own research (you are going to do you own research, right?)
To avoid disappointment or steering you in the wrong direction, we bolster our own experience with conversations with experts, comb through reviews on retailer sites & sales data, review industry publications, other blogs, and otherwise surface the best information available.
We aim for all thriller, no filler, as they say.
When considering dedicated .300 Blackout magazines, you have options.You can keep using your 5.56mm magazines, but identifying .300 BLK from 5.56 will be difficult without a means of avoiding cross-loading and the damage that can do to yourself or your firearms.
With a little bit of forethought, this can be done with something as simple as a paint pen and a few minutes of your time.
A better solution is picking up some dedicated .300 Blackout magazines; our favorite manufacturers already make many options that will work well and are dedicated to .300 Blackout. However you solve for it – good luck at the range and stay safe!
- Magpul, Magpul Dot Matrix Diagram
- Sporting Arms and Ammunition Manufacturers’ Institute, Inc., Voluntary Industry Performance Standards for Pressure and Velocity of Centerfire Rifle Ammunition for the Use of Commercial Manufacturers, December 14, 2015
- C.I.P., 300 AAC Blackout, May 18, 2016
- AR15.com, Magpul feed lips warping or cracking
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