Gun Digest

Measuring Up: Brownells Magazine Feed Lip Gauge

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The Brownells feed lip gauge is compact, sturdy, handy and lets you track your magazine wear.
The Brownells feed lip gauge is compact, sturdy, handy and lets you track your magazine wear.

Feed issues with your AR? Brownells Magazine Feed Lip Gauge to the rescue.

In the old days, we knew nothing about AR-15 magazines. They were mysteries. You kept the ones that worked and ditched/sold/traded the ones that didn’t. No one knew why this particular mag worked in my rifle and not yours, and vice-versa.

Life is so much better now, because we have magazines that work in all rifles … or do they?

One way to learn more is to measure things. However, measuring AR-15 magazines is difficult, because those who make them won’t tell us what they should and shouldn’t be. Good luck prying that information out of them; some might be helpful, and some might not.

Here’s the skinny:

Hmmm. That really isn’t as helpful as we would like, is it? And what really matters is that they be parallel, even, unbent and equally level along their lengths.

Brownells Feed Lip Gauge To The Rescue

Brownells offers its Magazine Feed Lip Gauge for those who want to track their magazines.

The gauge has two measuring surfaces that are managed by means of machining the gauge so the measuring part is a tapered bar. Strip the magazine (or just shove the gauge in; I’m too lazy to take them apart) and see if the gauge passed through the lip gap.

If it passes all the way though, the lips are too far apart. The magazine fails inspection. (Of course, if you’re heavy-handed, you can force the gauge through the mag lips, because, after all, they’re just aluminum.) If the bottom of the taper-to-the-small-dimension part won’t pass between the feed lips, the gap is too small, and the magazine fails. The test is simple enough.

Even so, here’s the rub: I have some (not many) magazines that fail the gauge but still work in my rifles. Oh well, life isn’t perfect.

Raise Your Gear IQ:

Track Your Training Mags

But, what you can do is track your training magazines.

You should have two sets of magazines. (Plus over-supply in inventory). Both sets have been tested, found 100 percent reliable and marked with your name, number, logo or whatever.

The Brownells gauge is compact, sturdy, handy and lets you track your magazine wear.

You keep one set stashed for TEOTWAWKI, or End of Days, or whatever it is you’re prepared for. They’re tested—but not used—and thus, not worn. They’ll be good for as long as you need them.

The other set comprises your training or competition magazines. These get used—and used hard. So, you test them and find they work. You mark them, measure each one, and record what they gauge at. Alternatively, once they pass the gauge, you can record their actual lip-spacing measurement.

In the regular course of taking them apart to clean them (practice and competition can get a lot of gunk inside of magazines) you check the measurement, or you use the gauge to check the gap.

I know, I know. This sounds like a lot of work. But here’s a secret: It’s what the top shooters do, and they do it with all their magazines—both rifle and pistol—when they take them apart to clean them. And, many shooters will even track the relaxed length of the magazine spring to see when it’s time to replace those.

Regular inspection will also uncover damaged magazines. Your magazines don’t always fall on the ground, hitting on their basepads first. Sometimes, they hit feed lips first. When that happens, they can get damaged. If you don’t look, you won’t know, and you’ll find out the hard way … most likely during a match. Cleaning gives you a chance to catch that damage and replace your training/competition magazine with one from your inventory (but not from your End of Days stock).

Yes, this can end up being a lot of effort on your part, but it’s the kind of effort successful people make.
And, as to the eternal question, “How many magazines are enough?” I’ll let you know when I get there.

The article originally appeared in the July 2020 issue of Gun Digest the Magazine.

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