Saturday, December 6, 2014

A few tips on large-capacity magazines

As part of my ongoing project to 'fix' and upgrade a number of AR-15 rifles for some disabled students and friends of mine, I've had to diagnose feeding problems.  Most of them have turned out to be related to magazines.  I thought my students, and perhaps other readers as well, might benefit from a short primer on the subject.  Note that most of what is said here refers to all magazines, whether for a handgun or a rifle.

The first and most important point is that magazines are relatively fragile items compared to the firearm itself.  They're typically made of stamped metal or molded plastic (sometimes both, as in Glock magazines, where a steel liner is surrounded by a plastic shell).  Some are stronger than others.  For example, US milspec ('military specification') magazines for the M4 carbine and M16 rifle (also used by civilians for their AR-15's, of course, and often referred to as STANAG magazines) are made of relatively thin aluminum.

STANAG magazines (image courtesy of Wikipedia)

If they're dropped on the feed lips, the latter can deform;  if they're trodden on, the magazine body will often dent or bend out of shape.  Once any of those things have happened, the magazine will become unreliable and should be discarded.  Of course, the military has ready access to as many magazines as it likes in its armories and supply depots, so this isn't a major factor for them.  On the other hand, some aftermarket M4/M16/AR-15 magazines have established a legendary reputation for toughness and longevity.  For civilians, who can't use taxpayer money to stock up on new magazines whenever we wish, such attributes are much more important than they are to the military.

Unfortunately, many shooters try to keep magazines in service even after they've become worn out or damaged, because they don't want to spend money on replacing them.  If you're playing games with your guns, I guess that's your call - it's not like your life's riding on your weapons system.  On the other hand, if you're trusting a firearm to preserve your life, you can't afford that attitude.  Many instructors with whom I've trained have opined that a quality handgun should have at least 4-5 magazines of equally high quality, to ensure reliable feeding and function.  I agree.  As for a rifle, the US military's standard-issue MOLLE load-carrying equipment enables the individual soldier to carry up to eight 30-round magazines of 5.56x45mm ammunition, or 240 rounds if they're fully loaded (of which more later).  That seems to me to be a perfectly good minimum - I say again, minimum - standard for how many AR-15 magazines a shooter should keep on hand:  at least eight good-quality, fully functional, tested and proven magazines per weapon.

(For both handguns and long guns, I personally prefer to have more magazines on hand than the minimum quantities mentioned above.  After all, what if you break or lose some magazines, or lend some to friends or relatives, only to find that resupply isn't immediately available?  Even worse, what if new laws restrict the sale or possession of larger-capacity magazines?  I'm sure many will choose not to obey such regulations, but they'll make it much more difficult to replace magazines as they wear out.  Having a few extra units on hand is cheap insurance [along with enough ammunition to load them, of course].  Furthermore, I retain older magazines for training and practice, so as not to unnecessarily abuse my newer 'defensive' magazines.  However, my background involves eighteen years in an environment of civil unrest and terrorism.  I freely admit that this has made me just a tad more sensitive about such things than your average American civilian, so YMMV.)

Choose your magazines according to your personal requirements.  I find the 30-round standard M4/M16/AR-15 magazine perfectly usable under most conditions, but when using a prone firing position they're a bit long, and can prevent me getting the rifle low enough to be comfortable (or less visible to potential opponents).  For that reason I like to carry a few shorter 20-round magazines as well.  On the other hand, some higher-capacity aftermarket magazines (such as the 40-round units available from several suppliers) are even taller than the 30-rounders, making it very difficult if not impossible to get comfortable or stay concealed when shooting from prone.  I've tried very-high-capacity (and much more expensive) magazines like the twin-drum 100-round Beta Mag or Surefire 60- and 100-round units, but find they make normally light and handy firearms much heavier and more unwieldy.  For a military unit wanting sustained full-auto firepower they make sense, but (IMHO) less so for civilian semi-auto applications.  I therefore choose to stay with standard-capacity magazines.

Bear in mind that manufacturers usually improve their products on an incremental basis, and this can affect your magazines.  For an example, see this discussion of Glock magazine follower generations.  As Glock pistols have moved from 1st, to 2nd, to 3rd, to 4th generation weapons, so their magazine followers have been incrementally improved as well.  If you have older magazines with very-early-generation followers, it might not be a bad idea to replace them with the current version (and new magazine springs while you're at it).  The US military has also improved the followers of M4/M16 magazines over time, so that there are three generations currently in service (being replaced, of course, by the latest version).  If you have older STANAG magazines for your AR-15, I strongly recommend upgrading the followers (I prefer Magpul's self-leveling follower for that purpose;  I've found it very reliable).

There's also the question of which generation of magazines works with which generation of weapon.  For example, Glock 4th-generation pistols have an ambidextrous magazine release catch that necessitates double notches on their magazines.  Those mags will work just fine in earlier-generation Glock pistols, but the single-notch earlier-generation magazines will not work just fine in 4th-generation pistols.  If you have Glock pistols from multiple generations, it's worth stocking only magazines that will work in all of them . . . because you don't want to find out the hard way, in an emergency, that this is a problem!

Sometimes aftermarket products offer significant improvements over original equipment.  Unfortunately, their quality varies from excellent to execrable.  I suggest you read the firearms forums to see who's buying (or not buying, or complaining about) which manufacturer or brand.  In my own collection, for example, I have nothing at all from ProMag or Triple K, but lots of magazines, accessories and related parts from (among others) Magpul, Mec-Gar, TangoDown, Troy Industries and Wolff Gunsprings.  (No, the companies I've named aren't paying or sponsoring me to mention their names.)

One can buy magazine upgrade or repair kits for many weapons;  but bear in mind that they all use the existing mag body.  If that's damaged or severely worn, it's often more cost-effective to replace the entire unit.  Besides, if one shops carefully, new magazines can sometimes cost less than repairing old ones.  For example, Troy Industries recently held an online Thanksgiving weekend sale in which a three-pack of its Battlemags (shown in Flat Dark Earth color on the left) was offered for $20 instead of the usual price of $42, with free shipping for orders over $100.  That worked out to less than $7 per magazine - a real steal!  (Yes, I got mine.)  It's worth waiting for annual sales events like that, and stocking up while prices are more affordable.

A word of warning:  unless you know and/or trust the seller, be careful about buying used magazines - particularly from gun show vendors.  For a start, they usually want exorbitant prices for their magazines.  Furthermore, they can't (or won't) tell  you who previously used them, for how long, under what conditions, and with - or without - proper routine cleaning and maintenance.  I'd rather buy new units, which can often be had for similar or even lower prices than many 'gun show commandos' want for their used stock.

As for keeping magazines loaded, this may be problematic in the medium to long term, for four reasons.

  1. Some weapons have trouble feeding the first or second round out of a fully-loaded magazine, because the pressure of the magazine spring forces the top round tightly against the bottom of the slide or bolt and prevents it being smoothly pulled from the magazine.  This usually goes away after the first couple of rounds have been expended.
  2. If the magazine spring is of high quality, it shouldn't have any problem;  but lower-quality springs can take a 'set' over time, where they don't regain their full range of compression and may exert insufficient pressure on the rounds for smooth, reliable feeding in a weapon, particularly the last few rounds in a magazine.
  3. If the walls of the magazine aren't sufficiently strong, they can bulge over time under the pressure of the spring on the ammunition in them, making them too 'fat' to fit into the magazine well.  First-generation Glock magazines without a metal liner were particularly prone to this.
  4. Over time, magazine feed lips can begin to separate under the pressure exerted by the spring against a full load of ammunition.  Magpul produced an innovative dust/impact cover for its second- and subsequent-generation PMAG's that reduced pressure on the feed lips, which was very useful;  but I don't know of any similar offering from other manufacturers.

To avoid those problems I routinely download my magazines by 10%, rounding to the nearest (lower) whole number if necessary.  A 30-round magazine will be loaded with 27 rounds;  a 20-rounder with 18;  a 15-rounder with 13;  and so on.  For long-term storage, where I anticipate leaving the magazine loaded indefinitely, I download by 20%, so that a 30-round mag will hold 24 rounds, a 20-rounder 16, a 15-rounder 12, etc.  This has eliminated from my weapons and magazines the four problems I mentioned, and I therefore recommend such downloading to all my students.  (Of course, if your weapons and magazines don't exhibit any of these problems, you're free to disregard those precautions.  YMMV.)

Magazines are often subject to greater abuse than the gun in which they're used.  For example, while training with instructors such as Massad Ayoob or at venues such as Thunder Ranch, I've dropped my magazines hundreds of times onto gravel-surfaced shooting ranges during rapid reloads.  The impact has dislodged or even broken more than one floorplate;  stones have scratched mag bodies;  sometimes someone's trodden on a magazine during fire-and-movement drills;  and dust, dirt, rain and mud have gotten inside them.  Furthermore, as dozens, then hundreds, then thousands of rounds go through them, magazines accumulate the same shooting detritus (propellant residue, excess lubricant, etc.) that one finds inside a dirty firearm.  However, few shooters (in my experience) clean and care for their magazines in the same way that they do their firearms.

I recommend that at least once per year (more often if they're hard-used or abused), magazines should be stripped down to their component parts and carefully checked.  The bodies should be cleaned inside and out;  springs checked for satisfactory performance;  and followers and floorplates examined to be sure they haven't been damaged.  Any worn parts should be replaced.  I usually apply a film of dry lubricant inside the magazine body before reassembly.  For magazines that will routinely be dropped during reloading, I also try to fit them with some sort of bumper pad on the floorplate to help absorb the impact and reduce the possibility of damage.  (For example, most of my more-heavily-used AR-15 magazines wear Magpul assists.)

Finally, I find it useful to segregate magazines according to mission.  For example, I have several older and/or lower-capacity Glock magazines reserved for training use only.  I make it quicker and easier to visually identify them by fitting orange Tangodown floorplates to them.  Also, if I want to reserve a set of magazines for a specific purpose or a specific weapon, I color-code them.  I learned the habit from a friend who has three AR-15-type rifles and carbines.  He's equipped each of them with stocks, grips and handguards in a different color (respectively black, flat dark earth and olive drab), and has a set of magazines in each of those colors reserved for each weapon.  Another friend uses different-colored Magpul assists to differentiate between different groups of AR-15 magazines.  Some people mark them with colored paint or tape, or allocate magazines from different manufacturers to specific weapons or purposes (such as loading them with a specific round).  The possibilities are limited only by one's imagination (and real-world practicality, of course).

In short, if any of your magazine-fed firearms has feeding issues, check the magazines first.  They're more often than not the key to the problem.



Bob Mueller said...

Great piece with good info. My only comment is that gun owners can't fall into the trap of calling a 30-round AR magazine "high capacity." It's not. It's standard capacity, according to the military.

Will said...

Normally, I wouldn't be concerned about leaving mags loaded. However, a couple years ago I ran into something unexpected.

There were two Colt OEM reduced capacity mags that were the type included with new rifles. Look like aluminum 20 rounders, but are internally blocked to limit them to 10 rnds. These were marked 7.62x39 on the bases, but otherwise appeared to be identical dimensionally to the 5.56 type. They had been loaded with a max amount of 7.62 (7 rnds, I think), for perhaps a year. The spot welds had failed, and the halves had separated enough at the feed lips end to make that end about twice as wide as normal. I think the base plate assembly was the only thing holding it all together. Both mags had failed identically. I would think the larger diameter of the Russian caliber would have less force (leverage) being applied to the magazine side walls, although it's possible the taper of the brass may have some influence.

I'm thinking it was a bad batch of mags, since a similar vintage set of 5.56 reduced cap mags did not fail while loaded for an identical length of time. These mags were probably made in the early 90's. Your thoughts?

Anonymous said...

Make an AR work; HAHAHAHAHAHAHAHA!!! The AR-15 is THE last weapon I'd ever stake my life on. They are not M-16's or even the M-4 jam-O-matic. AR's suck.Short AR's are worse. If I ever have to haul a "go to war" rifle I want something that will drop a man or beast graveyard dead at 400 yards, and AR's(and SHORT AR's) ARE NOT the weapons that can do that. The "range Barbie" is a nice toy, but nothing more. IMO. If, G_D forbid, we ever need rifles to defend ourselves in the US, a lot of men(and women) will die thinking "I wish I had something better than this worthless AR-15"---Ray

Peter said...

@Ray: I used to think as you do, particularly after South Africa tested early-generation M16's in the late 1970's and found them severely wanting in the hot, dusty African combat environment. However, the design has been incrementally improved since then, and today M4's and M16's have proved themselves reliable and effective weapons. Of course, the 5.56mm cartridge has limitations of its own, but those are independent of the platform, and ammo selection can help to at least partially compensate for them.

The M4/M16/AR-15 platform is today by far the most widely deployed military rifle in the Western world, including by special forces who can pick whatever they want (not just US units, but British and Israeli as well). I suspect that says a great deal about its combat utility.

tsquared said...

Great article. There is one point I would like to make about the polymer lowers used on some AR platforms. They will work fine with any metal magazine but a poly magazine will bind easily and be very difficult to lock in and to remove. Bushmaster's stance on their Carbon series is to use only metal magazines.

BTW: Ray if you have a jam-o-matic AR it was probably put together wrong by somebody who didn't know what they were doing or it had crappy parts to begin with. I have "been to war" and the M4 can drop a shithead at 400 yards without any problem by someone who knows how to use it.

John in Philly said...


Yes to taking care of your magazines.

Some thoughts on loading magazines to capacity.

I usually load no more than 26 or 28 rounds in a 30 round magazine, easier on older hands. (and the carpal tunnel.)

And as we know, the AR lacks a loaded chamber indicator. If we get in the habit of loading our mags with either a consistent odd number of rounds or a consistent even number of rounds, then a quick check to find out if a round chambered, is just to pull the mag and feel if the top round has swapped sides. (not my idea, but I think it is a good one.)

And lastly, as much as I liked the M-14 when the farthest I had to carry it was from the bow to the stern of a sub tender, the Emory S. Land's practice of loading only 5 rounds in a 20 round magazine was extreme even by Navy standards.

John in Philly

MrGarabaldi said...

Hey Peter,

Awesome article and your comment about not "Maxing" out the magazine is spot on. I always keep a couple of rounds shy of full capacity. Also when I was in the service, I would add a couple of tracers to the bottom so when I hit tracers, I knew that I will need to do a magazine change.
I took an M16 platform to war and had total faith in it. I knew that it worked well.

Will said...

I suspect the AR carbine, with the 16" barrel, has better cycling capabilities than any other version of the AR platform. The length of barrel between the gas block and muzzle determines the impulse time length of the gasjet that pushes the bolt carrier to the rear.

The shorter it is, the more critical that all parameters be as close to optimum for reliability. I don't recall seeing any data on what the various factors are in this regard. How far away from the chamber that the gas port is, is a complicating factor.

Anyone know where I can find relevant info?

Peter said...

@Will: Here are four good articles explaining the AR-15 gas system. The last is the most technical - scroll down to find graphs of gas pressure, etc.

As for your earlier question in your first comment (sorry, I didn't see it before), I agree - that must have been a bad batch of mags. I can't think of any other explanation. I'd be interested to know whether the same problems occurred later in life with the 5.56mm. versions from the same production run.

Inconsiderate Bastard said...

It may have originated somewhere else, but I give Tam credit for popularizing it:

When asked "how many magazines should I get" her answer was "more."

Firehand said...

Hadn't heard of Blue Works before, will have to check it out. I've been using Eezox for things line inside magazines, it seems to work well.

An AR expert I'm not, but Chris is, has a couple of posts on the subject of reliability:

Anonymous said...

For my recent AR build in 7.62X39, I bought a half dozen CPD 10 rd mags.
I encountered difficulties stripping the 1st round, attributed to excessive spring pressure. After storing the mags fully loaded for a month or so, they fed much better.
Another issue I noticed was that the cartridges were slightly tip down in the mags, so would hang up on the feed ramps of the barrel extension.
This I believe is due to the case taper of the X39 cart.
Rather than attempting to modify the feed lips, I removed the baseplates, and reversed the springs so the top coil contacted the FRONT of the follower, not the rear as supplied.
I also trimmed about 1/2" from the bottom of the front follower leg. This allowed a slight upward tilt to the bullet nose which improved feeding considerably.


Anonymous said...

Just a FWIW comment. Magazine mfgrs. are sometimes better (or worse) at making them for one firearm than for others. And their quality can vary from lot to lot. ProMag is a good example; I wouldn't have their mags for a lot of things, but the 10 and 20 rd. mags they were making for Ruger's Mini-14 seven years ago proved to be as good (and occasionally better than) the Ruger "factory" mags. I've never had a Ruger mag fail me, and that lot of ProMags have been just as faithful.


RHT447 said...

Just today got to wandering around this part of the sidebar, and thought I would add this---

Lots of good info at the link below. Obviously the site is centered on NRA Highpower Rifle. Still there is a ton of info in articles that are all PDF and downloadable for free.