Over the years, I have gone through many magazines. Some have been tossed away while others have been in my collection for longer than I can remember. Despite the fact that I probably have more magazines than I could ever use, I still continue to buy more, experiment with new brands and styles, and even buy more of the ones that I already have. There is a great amount of variety when it comes to AR-15 magazines and in general, it’s really not hard to find a good magazine. However, with options come arguments about what is better and why. About 5 years ago, TFBTV presenter Alex C stated his case as to why he didn’t use Magpul PMAGs. At the time I thought nothing of it since I didn’t own the type of guns he had access to and generally didn’t run into the same problems as he did. However, some recent research and experience have changed my mind about how I look at AR-15 magazines, and perhaps what I’ve found might change your mind as well. Can we truly answer the question about which AR-15 magazines are the best fit for your AR-15?

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Are Aluminum Magazines Still the Best Fit for the AR-15 Platform?

As with anything in the firearms industry, there is a lot of variation between manufacturers as far as exacting dimensions go. Before starting any of my testings, I took a sampling of my various AR-15 magwells to get a read on what the average width was between all of them. I found the smallest of my AR-15 magwells to be right at 0.92″ wide while some of my wider ones ended up being around 0.94″ at the widest point not including any flares. While that may not seem like a huge variance, it will come into play later and it is still something to consider when determining what the best type of magazine to run in your rifle is.

The impetus for this research came about one day when I went to perform a magazine change and the magazine didn’t drop free. While this isn’t a huge problem in and of itself but it still stuck with me after my range trip and I then started off down the path of attempting to discover if other magazines did this. Some research has been done by people online to determine if your magazines can be stored loaded without worry and for the most part it seems like aluminum mags tend to fare better than polymer ones. The combination of heat and time will tend to stretch the upper end of the magazine so wide that they are difficult to seat in an AR and also won’t drop free sometimes.

I won’t get into reliability testing, Matt E already did that a couple of years ago and had some pretty convincing arguments as to why the Magpul Gen 3 P-mags and Hybrid Lancer mags are superior in this regard to aluminum and steel magazines. What I aimed to find out was which magazines fit the best with the AR-15 platform in general.

Many Magazines, Many Dimensions

In total, I tested 11 different types of magazines from run-of-the-mill mil-spec aluminum magazines to the latest Gen III P-mags. Before measuring everything, I took all of my unloaded magazines and made sure they were seated and dropped free in three different AR-15s. Every single one did and there are really no surprises there as I think most magazine manufactures wouldn’t let something out of the factory if it didn’t at least appear to work.

Moving on from there, my testing procedure was as follows. I measured the magazine at its widest point at the top unloaded, recorded the measurement, and then proceeded to load the magazine up with 30 rounds. After being loaded I took a second measurement at the same exact spot and then tested the magazine to see if it would seat and drop free without issue. Simple enough right? The data I collected is listed below.

Conclusions

None of these magazines are new and each of them has been used at least one or more in their lifetimes. The outliers in this group above revealed the following (please let me know if you picked anything else interesting from this limited data set). The ProMag Rollermags wouldn’t accept the full 30-rounds without great force. This led to the lips of the magazine expanding to well over the .94″ width that my widest AR-15 magwell and even when down loaded to 29-rounds the magazine would still not drop free – I wasn’t able to forcibly seat the magazine in either of my two other AR-15s which measured 0.93 and 0.92″ in width.

Aside from the Gen I P-Mags, the PMAGs performed just as well as all of the aluminum mags with the lips only expanding by about 0.01 inches after being loaded. I can assume that environmental factors and time would cause this number to rise slightly with the P-mags more than the aluminum mags. The Troy Mag didn’t fare much better and expanded 0.04″ total and ended up not dropping free from 2/3 magwells without being down loaded to 29-or fewer rounds.

While this data might not make or break your decision to go with polymer, aluminum, or steel mags, I still felt that it was relevant enough to share with all of you. It’s good to keep in mind that the AR-15 platform is based on a military weapons platform and that magazines designed for the AR-15 were initially designed to be disposable and inexpensive. While it took decades, the US Military eventually transitioned from aluminum magazines to Gen III P-Mags which have thus far proven to be extremely reliable and will fit with their rifle systems. Since we aren’t in the military we have the convenient option of matching the magazines we like to the rifle we like and we don’t have to rely on what’s handed to us.

I’d like to hear your experiences with various types of magazines down in the comments below. What is your favorite type of mag and why? Have you switched the types of magazines you use in your rifles recently? Thanks as always for reading TFB.

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