What, if anything, happens to an AR-15 magazine if you leave it loaded for years? I’ve seen a ton of debate on the internet, so back in 2014 I decided to run a test. I loaded two Magpul PMag’s, setting one aside to test in five years, the other set aside to test in 10.

Five years is up, so how did the magazine do? Let’s find out.

Magpul M2 PMag

The magazines I am using are Magpul PMag M2 with a dust cap over the mouth of the magazine.

This dust cap also slightly depresses the rounds in the magazine which takes pressure off of the polymer feed lips, in addition to keep crud out of them.

There are 5 basic parts of a Magpul polymer magazine. They include the outside shell, the follower (the part the bullets sit on), the spring, the spring base and the magazine base.

When it comes to storing ammo in magazines long-term, the two biggest concerns in the prepping community seem to be whether keeping a spring under load that long will weaken it, and whether leaving that much pressure on the feed lips will cause them to deform.

As mentioned above, the cap depressurizes the feed lips, but it does so by increasing the compression of the spring even more than if the cap were not in place.

The Full 30

Although I normally only load 28 rounds into a 30-round magazine, for this test I wanted to give it as big of a challenge as I could. I loaded it with 30 rounds of steel-case ammo

Let’s look at how the five parts held up

Two of these parts can just be ignored, as the follower and the spring base basically are just plastic pieces sitting there doing nothing.

The magazine bottom also can at least mostly be ignored, but since it is under pressure and it could have bulged, becoming difficult to remove, I’ll mention that it didn’t.

The body got a bit scraped up over the five years of sitting in a drawer. It went into that drawer at my house on September 10, 2014 along with it’s 10-year buddy, so it’s picked up a few marks. The feed lips look perfect, however.

The spring looks good, and most importantly it measures the same length as other second and third generation Magpul springs. Once I figure out a way to measure the pressure of the spring, I’m going to include that in an update to this article.

The spring on the left is the 5-year Gen 2, while the spring on the right is a newer Gen 3.

Again, the test magazine Gen 2 is on the left and a Gen 3 with window is on the right. The orange painted section is so you can see the “rounds left” indicator.

The Test: How did it shoot?

We shot the magazine dry at the range today, following a full range session in a Del-Ton M4 wearing Magpul furniture (more information about this gun is available by clicking HERE!).

The rifle was hot (as in far too hot to touch) and it’s far from a premium AR, so I thought it would be a good test.

The magazine seated nicely into the mag well, took the first round into battery, then Spice proceeded to drill one two inch hole in a piece of paper downrange (one 1/2 inch off flyer). The magazine (and gun in general) operated flawlessly shooting steel cased rounds after a day’s worth of shooting rot-gut Tula steel.

Bottom line

As far as I can tell, there were no adverse effects from loading up this magazine and leaving it stored full. It will be interesting to see how the 10-year magazine does as well as a 5-year AK-47 magazine that will ‘”come ripe” next month.

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