I tried to answer that question in general terms a couple of years ago, but it's recently been raised again in e-mail conversations with a few readers. I thought it might be a good idea to get specific in terms of brands and versions that I have personally tested, and trust. Obviously, there are many more brands out there, but unless and until I've checked them out myself, I'm not going to recommend them. YMMV, of course.
My top choice, hands down, is the Magpul 3rd generation PMAG. This has just been selected by the US Marine Corps as its standard-issue combat magazine, which speaks volumes, IMHO. (The USMC will continue to use the 'traditional' metal STANAG magazines for training purposes.) The G3 PMAG has several improvements over earlier generations, including being certified to work in several weapons where the G2 PMAG exhibited problems (such as the HK 416 and the M27 IAR). These and other issues had led to the G2 PMAG being banned by the US Army and USMC in 2012, but the G3 resolves them. The G3 also feeds newer types of 5.56x45mm. ammunition, such as the US Army's M855A1 and USMC's Mk. 318 Mod 0, without any difficulty.
The PMAG is available in 20, 30 and 40-round sizes in 5.56x45mm, and in other cartridges as well. (I find the 40-round size to be too long - it gets in the way when shooting from a prone position. I prefer 20-round magazines for prone use, and 30-round for general-purpose use.) The PMAG comes in two versions; one with solid sides, the other with windows in the sides allowing you to see the rounds it contains. If you shop around, the G3 PMAG can be purchased online for between $11-$15, with the windowed versions usually (but not always) one or two dollars more expensive than the plain ones. They're available in black and flat dark earth, and also in a sand color that's specifically designed to work with Rit dyes, so you can color them any shade you want.
I have a number of sand PMAGS dyed in colors that suit me, including a few 20-round versions in a bright red to indicate ready-use expanding ammunition in my gun safe. (I even dyed a couple of 30-rounders in passionate purple, to accessorize Miss D.'s purple AR-15).
My second choice is the Troy Battlemag. I think this is a good design overall, with a couple of advantages and a couple of drawbacks. Advantages include:
- The magazine is thinner side-to-side than either the PMAG or the L5AWM (discussed below), and its baseplate is narrower. This means you can fit 2 or 3 Battlemags into magazine pouches that won't accept the same quantity of the other, fatter, magazines.
- It's slightly lighter than the PMAG or L5AWM. If you're maxing out your load, and every ounce counts, this might be important.
- It comes with a built-in magazine 'pull tab' assist, making it easier to extract from a mag pouch if you're in a hurry. If you don't want to use the tab, you can replace it with a flush-fit floor plate (included). On a PMAG or L5AWM, fitting a mag assist or a ranger plate to do the same job is an extra-cost option, whereas it's free with every Battlemag.
- The Battlemag's plastic appears to be softer and more pliable than that used in the PMAG or L5AWM. This has not proven to be a problem in my use of the Battlemag thus far, but if you intend to leave magazines in storage, loaded, for a long period, I think the feed lips might stretch or deform. I obviously don't know this for sure, but it's a factor to consider.
- The Battlemag design incorporates an internal rib running down the front face of the magazine, fitting into a notch on the follower. It's been reported from several sources that this prevents the use of .300 Blackout ammunition, which is 'fatter' than the 5.56x45mm. round for which the Battlemag is designed. Obviously, if you only intend to use .223 or 5.56 rounds in the magazine, this is no problem at all; but if your magazines might have to do double duty with the larger cartridge, the Battlemag is probably not a good choice for you. (No problems have been reported using .300 Blackout ammo in PMAG's or L5AWM's.)
Those reservations aside, the Battlemag is plenty tough enough for serious use. Caleb Giddings of Gun Nuts Media actually shot one and then tested it, with impressive results.
Other sources have also provided satisfactory feedback about the Battlemag. They can be expensive, but if you wait for a sale by Troy Industries, you can sometimes pick them up at excellent prices (as I did, a couple of years ago - at under $7 apiece, they were an absolute steal!).
Lancer L5AWM (shown at left). This has attracted favorable attention from many sources, although as far as I know it's not been adopted by any large-scale military or law enforcement agency or service. It's available in solid colors, or with smoke or clear sidewalls. I'd rate it as superior to the G2 PMAG, although not to the G3. I only have three of them at present, as they're usually not as widely available as PMAG's, and are often more expensive; but if I had the chance to get some at a comparable price to PMAG's, I'd have no hesitation grabbing them. Given more experience with them, they might move up to second place on my list of desirable magazines, as the plastic from which they're made seems heavier and more durable than that of Troy's Battlemag. We'll see.
My fourth choice, which is also still under evaluation, is the ETS AR-15 magazine. This is available in clear or smoke finishes, and with or without a coupler device allowing two magazines to be linked together. Here's a brief video showing how easily the coupler can be used.
I've bought a few of the ETS coupler magazines for evaluation, and will be testing them over the next few months. I like what I've seen of them so far, and if they continue to perform as well as others have said, I'll probably buy more of them and add them to my magazine rotation.
There are many more makes and models of AR-15 magazines out there, but the four I've mentioned above are those I've actually tested for myself, and am therefore prepared to recommend, in the order listed. (I also have several dozen STANAG military magazines, ranging from very old to fairly new. I've refurbished them all by installing Magpul magazine followers, new magazine springs, and new floor plates. I use them primarily for training.)
I hope this helps answer my readers' questions on the subject.