Gun Tests magazine tested AR mags in its May 2014 issue. The Brands included CAA, IMI, SWT, OKAY, NHMTG, Magpul (windowed and plain) Cammenga, Brownells, Sig Sauer, ProMag, Troy and Thermold. They determined price has little to do with quality - the opposite you typically find with guns and gun-related products.
Ten 30-rd mags were polymer - Command Arms Accessories ($12.34), IMI Defense ($11.97), ProMag Industries ($15.45), CAA Countdown Mag ($13.52), Sig ($20.00), SWT ($17.99), Thermold Master Molder ($10.59), Troy Industries Battlemag ($14.29), Magpul PMag Gen M3 ($14.20) and Magpul PMag Window Gen M3 ($17.05).
Five other mags were metal body units - Cammenga Easymag ($21.99), ProMag Blue Steel mag ($18.31), OKAY Industries USGI ($8.99), NHMTG MA02L 20-rd ($19.99) and Brownells Gray mag w/SS spring ($9.99).
Prior to the torture test, Gun Tests staff used a Brownells magazie lip gauge to ensure the magazine lips were in spec. Brownells technicians warned them that the gauge may not be applicable to poly mags, but they tested each with he gauge before and after the test. The mag lip gauge had to enter the space between the feed lips with light pressure - it could not simply drop into the space between the mag lips.
For function tests, they used two proven firearms - a Daniel Defense rifle and a Bushmaster standard carbine. The rifles were well-lubed during the tests. Neither rifle, both with more than 3k rounds through them, had ever exhibited a malfunction of any type in the past.
Test 1 - With unloaded rifles, they inserted an empty mag to check for fit and lock.
Test 2 - they inserted loaded mags into the rifles to be certain they locked correctly. Next, they pressed the mag release to make certain the mag dropped freely. They also carefully worked the bolt to make certain the first round loaded cleanly.
Test 3 & 4 - Using fully-loaded mags, they dropped each mag down a tube to control its orientation. (No height was given, but I would assume it was 3-4 feet. The surface appears to be concrete) First, they dropped the mags on the lips, then on the base. Each mag was dropped three times. If a round was lost, it was replaced for subsequent drops. They noticed many bullets were pushed back deeper into the case. Some cases were dented and crimps were broken from the force. Those rounds were tossed.
Of the eleven types of mags that continued the test at this point, the PMag window and Brownells mag lost only two total rounds. The NHMTG 20, NHMTG 30, OKAY, PMag (non -window) and SWT lost a total of three each. The Sig lost seven, the Thermold lost eight, the Troy lost nine and the CAA Countdown lost 13.
Test 5 - A 210-pound tester wearing Danner jump boots leapt from a 3.5-foot platform onto each mag. He was attempting to hit dead center. (It is not clear if the mags were loade or unloaded) after this test, the mags had to lock into the rifle, eject normally and feed the first round reliably. All mags passed this test.
Test 6 - The GT crew slowly ran over the loaded mags with a Chevy Corvette and a Ford 4WD Ranger. Three mags lost rounds and received deductions - the CAA Countdown, Sig and SWT. The mags did, however, remain functional.
Test 7 - The surviving mags were loaded with a full compliment of Tula steel case 55 gr FMJs and dropped in soupy mud. They picked up each mag, shook it dry and rushed it to the muddy range for a test firing. The CAA polymer mag failed to feed in this test and was eliminated.
Test 8 - They reloaded the mags with Remington 55 gr FMJs and left them submerged in water for 24 hours. They then drained them and checked for spring corrosion and function. This did not affect function.
Test 9 - They let the unloaded mags cook in full sunlight for a day. None changed shape or configuration. All locked into the rifles.
Test 10 - They loaded the mags with steel cased ammo and placed them in the freezer for 24 hours. No water was involved.
Test 11 - The mags that survived the physical tests were subjected to rapid fire with three different types of ammo.
Here are the grades:
CAA 30-rd polymer (Cheaper Than Dirt $12.34): F
It fell apart on the third drop onto the feed lips.
Cammenga EasyMag (Impact Guns $21.99): F
This mag did not pass the drop test when it's sliding front door opened and dumped the mag load.
IMI Defense (Cheaper Than Dirt $11.97): F
This mag failed the drop test by losing the ammo load on the first drop. The drop cracked the mag body.
ProMag Blue Steel (PromagIndustries.com $18.31):
The feed lips were crushed in the drop test. Rounds could not be loaded without a screwdriver.
ProMag Black Polymer (PromagIndustries $15.45): F
This mag lost 2, 10, then all rounds in the drop test. The mag was croaked and non-functional after the test.
CCA Countdown (Cheaper Than Dirt $13.52): F
During the firing test, this mag failed to properly feed. This mag also lost many rounds in the drive-over test.
Sig Sauer (Cheaper Than Dirt $20): B
This mag also lost a lot of rounds when driven over, but made it to the firing test and passed.
SWT (sportsmanguide.com $17.99): B
A well-made mag that sailed through early testing. It lost a lot of rounds in the vehicle test, but passed the firing exam.
Thermold (Cheaper Than Dirt $10.59): B
It was one of the cheaper mags, but did well overall. It did, however, malfunction with steel cased ammo.
Troy (Midway USA $14.29): A-
The Troy is a very well-built mag. It lost out to the OKAY, NHMTG, Magpuls and Brownells because it lost more rounds in the drop test. It lost zero rounds in the vehicle test. It is robust and reliable.
OKAY (gunsamerica.com $8.99): A-
This mag gave excellent results.
NHMTG 30-rd MA02L (brownells.com $19.99): A
The 20-round mag also did well, but was no longer available from Brownells. These mags tied with the OKAY, Magpuls and Brownells by a narrow margin. Function was good as was reliability.
Magpul PMag Ar15/M16 Gen M3 (brownells.com $14.20): A
The PMags were the top performer among polymer mags. Ease OD disassembly, reliability and general handling were a big plus.
Magpul PMag Window AR/M4 Gen M3 (brownells.com $17.05): A
Surprisingly, the windowed PMag performed slightly better than its non-windowed brother. When run over, neither this mag nor its window cracked.
Brownells 30-round Gray: (brownells.com $9.99): A
These mags are very similar to the ones Brownells supplies to the US Mlitary. All components are mil-spec. These mags are affordable, tough, well-made and reliable.
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