It’s not easy choosing the best 300 blackout magazine AR-15 rifles if you’re not clear on what to look for. So many people use the standard 5.56 mags that they forget it’s not the optimal-performance choice. Take a look at some of the best alternatives on the market and select something that will make your life easier and your shooting more reliable.
- Lancer Systems L5AWM 300BLK
- Magpul PMAG 300 BLK Gen M3
- D&H AR-15 300 BLK Mag
- Daniel Defense AR-15 5.56 Mag
- Hexmag 5.56 Mag
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Can You Use 5.56 Magazines for 300 Blackout Rifles?
Yes, you can. It’s a common misconception that you can’t—the reason being that 5.56 rounds don’t go well with 300 Blackout chambering.
It’s not uncommon for a 5.56 round to cause blocking or even an explosion. However, 300 Blackout rounds will fit inside some 5.56 magazines. Hence, you can use them in your BLK rifle.
But is it the best choice? Not really.
300 BLK rounds are usually longer. They also align differently in the magazine, so using a 5.56 model often causes problems with loading speeds and pinching.
Long before polymer, there was steel and aluminum alloy. I’d like to think that both have their unique advantages.
Yet, it seems that in most cases, polymer has a significant advantage. It’s a more versatile material capable of presenting impressive durability.
The resistance to the elements is far superior by any standards. That said, a combination of both often yields the best results.
Where it matters is in the feed lips of the magazine. A reinforced steel component is less prone to warping than a polymer alternative. This is not merely a matter of personal preference; it’s about what excels in the long run.
What is essential to look for is any tolerance stacking issues. It’s something that plagues most polymer magazines because they tend not to cater to any specific make of AR.
Several things can help you compare and differentiate the quality of various models. For one, you have the round capacity. You can usually choose 10-, 20-, and 30-round magazines.
But it’s also possible to opt for 32-round 5.56 mags for your 300 BLK rifle. Again, it comes down to preference and how much you trust a 5.56 mag’s performance with 300 BLK bullets.
The best blackout magazine may also come down to grip for some users. You don’t fire under the same stress and weather conditions all the time. A superior grip may be more important than patented internal geometry or a fancy follower.
Round visibility is something I take very seriously. Sometimes, I make do with windowed magazines without a problem. But, if I’m honest, I prefer see-through mags. Nothing provides a better-unobstructed view of your rounds.
However, keep in mind that not all translucent polymer mags offer the same long-term durability. This is usually when the manufacturer’s experience comes into play.
Last but not least, you’ll want something easy to reload with and take apart for maintenance. Again, this is an area where I feel only a handful of 300 BLK magazines exceed expectations.
Best 300 Blackout Magazines
The L5AWM 300BLK is one of the most reliable magazines for the AR-15 platform. The translucent smoke finish looks impressive, and the design borrows a lot from the company’s original one.
One of its unique features is a non-tilting follower that caters specifically to the 300BLK cartridge. You’ll notice the 30-round capacity and superior durability.
The combination of steel and polymer makes this a highly-resistant mag to corrosion and chemicals. You can use it in all weather conditions. I also like the aggressive texturing as it provides an excellent gripping surface, with or without gloves on.
You may also appreciate the hardened steel, coated feed lips. It should address one of the common vulnerabilities of AR-15 mags. I know I’ve dropped a few in my day, and alloy feed lips rarely add to the structural integrity.
I also recommend the L5AWM mag for its slide-on base plate. It makes magazine maintenance so much easier without affecting the overall durability. Between its smooth feeding and on-point interior geometry, the L5AWM is perhaps the best magazine for 300 blackout AR-15s.
Although Lancer 300BLK magazines come in three sizes, I recommend going for the 30-round capacity mags. They give you sustainability on the range and allow room for error.
- Hardened steel feed lips
- Sliding base plate
- Ultra-durable construction
- Great grip texturing
- Feed lip sleeve may still warp after extended use
Another 300 Blackout magazine designed to increase the performance is the PMAG 300 BLK Gen M3. Magpul does a great job with this mag, especially on its internal geometry.
The unique design accommodates the largest variety of profiles used in 300 BLK cartridges. I also like the clarity of the BLK marking. It does make mixing these up with 5.56’s almost impossible.
What I like most about this model is that it doesn’t cause bullet pinching. That’s a common issue with 5.56 mags. By using a slightly smaller follower, Magpul addresses the issue of 300 BLK bullet alignments.
It results in a smoother and faster feeding process. No one wants to use a rifle that loads slower than intended. And that can happen if you use 5.56 mags in a Blackout-chambered AR-15.
But not everything’s great. Personally, although I love this magazine design, I also prefer to see the round count. Magpul doesn’t even use a windowed design. In my view, this takes away from its overall appeal.
The polymer feed lips do a good job, better than most of their alloy counterparts at least.
- Perfectly calibrated interior
- Loads faster than most
- Clear BLK side marking
- No pinching issues
- Can’t see the number of rounds left
- No special grip texturing
Instantly recognizable, the D&H 300 BLK magazines come with a red follower. It doesn’t matter which model you choose – 10, 20, or 30-round capacity mags.
This is among the most affordable mags in this category, partly because of their aluminum body. But what truly sets these mags apart is their longevity.
No, they’re not the most durable on the market. But they did come well before the offerings from Lancer and Magpul. It’s also evident given the use of aluminum over polymer.
That doesn’t mean that old is necessarily bad. The internal geometry of these mags still caters to the 300 BLK chambered rifle. And if you burn through ammo like crazy, having something cheaper on hand isn’t a bad idea.
That said, I’d like to point out that these aren’t always reliable. The main reason is the proprietary red tilt follower. It does a great job at preventing pinching and bullets from getting stuck.
However, the opposite orientation may create some problems down the line. All in all, it’s still a great mag for beginners or budget-minded AR-15 owners.
- Correct internal geometry
- Ideal for medium grain 300 BLK bullets
- Windowed design for bullet tracking
- No pinching issues
- Weird opposite orientation for the follower
- Full aluminum alloy build
You know by now that the best magazine for 300 Blackout rifles is usually one that caters to the BLK chambering. But this model from Daniel Defense offers an interesting alternative.
BLK AR-15 rifles shoot 5.56 rounds just fine. It’s an issue of min-maxing if you opt for BLK-specific magazines and ammo.
For example, this choice may pose some minor accuracy issues. But the magazine itself features an excellent design. The anti-tilt follower offers reliable feeding.
The bottom plate has an impact-absorbing design that increases the longevity of the mag. I also like the fact that it holds 32 rounds instead of 20 or 30. It’s not my personal favorite, but I may still use it on occasion for the extra two bullets.
I also like the reinforced polymer construction and hardened feed-lip. The disassembly process is also a no-brainer. I recommend this model for those using 5.56, 300 BLK, and even 223 Remington ammo.
It’s an all-around performer. And despite its higher price tag, it serves people that want more variety. There’s also a small textured surface on the front of the mag. This should help address some grip issues in very hot or humid weather.
- Compatible with 300 BLK and 5.56 NATO rounds
- 32-round capacity
- Impact-absorbing design
- Textured surface
- Not optimized for 300 BLK rounds
- Windowless design
It wouldn’t feel right if I didn’t also offer the ultimate budget option. Hexmag 5.56 magazines are among the cheapest you can find.
It’s not the most popular brand on the market, yet its offering provides an interesting alternative to the top of the line competitors.
First of all, these magazines feature a polymer construction, which is something I didn’t expect to see in this price range. The manufacturer also offers a variety of HexID followers in various colors.
It’s a nice perk if you want to color-code your 300 Blackout mags. The anti-tilt follower does an excellent job at preventing pinching and improves the feeding time. I also like the textured grip, as it covers most of the magazine.
The flared base plate is a nice touch, although nothing too special if you ask me. Granted, these Hexmags may still cause some of the standard issues when using 5.56 rounds in a Blackout AR-15.
If you’re looking for affordable options, I recommend testing this one out first yourself. It does a lot of things right, but it might not feel great for everyone. I also think that the pricing reflects on the overall durability.
- Very affordable
- Follower color coding available
- No pinching issues
- Great textured exterior
- Polymer feed lip
- Average durability
Final Thoughts and Recommendation
After careful consideration, it’s hard to look past the Lancer L5AWM 300 BLK magazines. Launched back in 2018, these magazines still feel like the standard all other Blackout magazines should live up to.
The superior durability of the feed lips and the option for a translucent build offer so much quality of life. It’s also great that the internal geometry of the mag caters to heavier grain ammo— something that not all direct alternatives seem to do.
The blend of polymer and hardened steel extend the longevity of these mags considerably. And I particularly enjoyed the slide-on base plate for maintenance purposes.