The absolute best mags I have ever used for an M4/M16 are the HK 30rd mags. Steel body w/ a steel anti tilt follower. They are expensive, $50-60~ a mag, but well worth the cost.
Just so you know, these have been having lots of problems as well. Some of it comes from the fact that they are designed for the British SA80 to correct that rifles problems.
There are two different series of HK mags. The first series is the one that was the ok set whereas the 2nd series was very problematic. Trying to remember the main way to tell them apart, but if I remember the HK product stamping that is finished in black is the second series. The second series also incorporated a rubber bumper/stop-type thing on the bottom of the floorplate.
Lots of people bought into them when they first came out. Then they started rusting. People began to sometimes have malfunctions after the mags had been dropped as the steel wasn't as elastic and forgiving as aluminum. There are a couple others, but I honestly don't remember as I just don't use HK stuff. I used to use an MP5 and I remember some of the customer service horrors that are involved with the company.
I stick with USGI or Magpul PMags. Lancer has the new translucent ones out as well. A few guys I know were doing some testing of them. They were nice, but most didn't see the advantages over the previous two that worked just as good for less.
Stay far far away from the Thermold ones....I've heard that they are starting production again.
