Loaded Magazine Confusion

[lysander]

1) Was there a control group?
2) Im curious what the results would be from unloaded mags.

1) Yes, brand new unused magazines.

2) Look at the graph. Triangles and squares . . . . X and O are loaded.

[davidjinks]

Okay, now I'm confused. On these two points I've read many convincing arguments that: 1) 30-round mags are meant to hold 30 rounds and there's no need to under fill them to insure proper function, and: 2) The springs wear out faster by repeated emptying and filling of the mag, as opposed to leaving them loaded. I've lately been reading the US Marine Corps Rifle Marksmanship manual and the following are excerpts pertaining to these two points: 1) "The recommended number of rounds per magazine is no more than 29. Thirty rounds in the magazine can prohibit the magazine from seating properly on a closed bolt." 2) "Ammunition in filled magazines should be rotated frequently if the rounds are not expended. The spring tension on the magazine can weaken if compressed for a long period of time and can cause a malfunction of the magazine." Hard to imagine the Marines have it all wrong...

My stored magazines for the day the world comes to an end and we’re fighting the antichrist are loaded with 28 rounds, stored in a .50 cal can with another reload for all 12 mags on stripper clips with spoons.

My chest harness that is setup for right here right now are loaded to 30 rounds.

Currently I have a spare chest harness in my OMG THE WORLD IS ENDING BOX! Harness holds 12 rifle mags, 5 pistol mags and an IFAK. I loaded the rifle mags 12 years ago with MK262. I just grabbed three of the mags 2 weeks ago and took them to the range. They all functioned and locked back the rifle every time. Zero feed lip spread and zero issues with mag springs.

Load your mags however you’re comfortable loading them. If you want 30 rounds, do 30. If you want 29 or 28, do that.

I have spare mags that have never been loaded and are a standby in case the day comes I have mag failures. I also have 12 mags that I have been using for training for the last 10 years, multiple classes, many many many range days. Never cleaned them. Never PMed them. They still function the same as the day they were new. I couldn’t even tell you how many rounds are on them nor could I tell you how many times they’ve been dropped on concrete and gravel. They just keep working.

[ViperTwoSix]

Not quite.

"EVALUATION OF PRETREATMENT PROCESSES AND LONG-TERM STORAGE ON MAGAZINE SPRING FOR THE M14, 7.62MM, RIFLE," LaRiviere, Feb 1966, Springfield Armory, MA

"PERFORMANCE OF 5.56-MM 30 ROUND MAGAZINES AFTER EXTENDED LOADED STORAGE," Foltz, Grego, Escalona and Ritschel, ARDEC, Picatinny Arsenal NJ

The purpose of this test was to determine if storing of a loaded 5.56-mm, 30 round tan follower magazine [part number (P/N) 13021312] with M855 ball ammunition for an extended period of up to 5 yr would degrade the magazine spring to the point that its spring force would not properly load ammunition into the host weapons: the M4A1 and M16A4. It is important that the magazine spring supply enough force to chamber the next cartridge properly, otherwise the weapon may misfire (ref. 1). . .

Beginning in April 2011, three hundred 5.56-mm, 30 round magazines were loaded with M855 ammunition. Prior to loading, each magazine’s spring force was measured in accordance with (IAW) DR 13021312, note 2, which allows the spring force when depressed 0.25 in. to be between 2.5 and 3.5 lb. Once loaded, all 300 magazines were placed in a storage bunker located at the U.S. Army Armament Research, Development and Engineering Center, Picatinny Arsenal, NJ. In 6 month intervals, over the 5-yr period, 30 magazines were removed from storage and fired, 15 on an M4A1 and 15 on an M16A4. The cyclic rate of the weapon was recorded as well as the spring force of the magazine when empty.

In a previous evaluation of long term storage conducted on M14 magazine springs, it was shown that the majority of spring force degradation due to extended storage occurs in the first two years, as shown in figure 1. Therefore, it is probable that if the 5.56-mm, 30 round magazines still fire properly after 2 yr of storage, then longer intervals of storage would not cause system failure since the majority of spring set would have already occurred (ref. 4).



There is a loss of spring load due to extended compression.

HOWEVER:

The minimum spring strength specified on the drawing IS NOT the the minimum strength required for reliable operation. Magazine springs can be considerably softer than the print minimum and still work fine. Think about it, they have to be otherwise many springs wouldn't work correctly right out of the box.

Also note the curves flatten out after the first two years, so it is only after two years that continuous compression that there is no further degradation of spring strength.

So, the next question: How many cycles to wear out a spring?

Well, the M14 test is try and answer this and configure a machine to compress about 20 M14 magazine springs from empty length to full magazine length. After 10,000 cycles the springs lost just over 3/4 pound of strength. Since the M16 magazine spring is a different material, there might be some differences in spring life.

Lysander, thank you for the technical correction. I learned something new today.