I had to store some new orders that had arrived recently. I figured since I had them out I might as well do a comparison. The comparison is between an HK AR-15, USGI by Bushmaster, and a MagPul PMAG all of which are 30 round 5.56x45mm magazines.
FYI: The C Products magazine by eyeballing it is the same or about the same as the Bushmaster. I did not bother with the Brownells magazine I got to test. It was a epic failure right out of the box. The follower gets stuck when pushed down. I am going to replace the floor plate, spring, and follower with MagPul products.
The HK magazine is the heaviest and largest of the the three. The HK magazine by my measurements is longer with a length of 19.3 CM. The PMAG is the second longest with a length of 19 CM. The USGI is the shortest with a 18.2 CM length. The PMAG is the lightest in weight of course, which places the USGI magazine as the second heaviest. Both the USGI and HK magazines are the same in width at 2 CM. The PMAG is just slightly less then 2 CM. Follower width is the about the same dimensions. I was having trouble pushing it in and obtaining the most accurate measurement I could do by hand with a standard ruler, but from what I can tell it is about the same.
FYI: I measured length from the bottom corner to the top ignoring the curve. I was using a standard foot long ruler.
Pictures: (Yes I know the cap was on the PMAG, but I took it off for measuring, which is noticeable as it was removed during pictures, which I took first.)
Lastly if you are curious of what I prefer, it is the PMAG. As far as metal magazines go I prefer the HK magazine. I received it this week along with the dark earth PMAGs. The HK I bought because Botach Tactical was selling the HK magazine for 30+ dollars. It was a impulse purchase as I have never seen them that cheap. The fit and finish is better then either C Products, Bushmaster, or Brownells, of which I have experience with only. The magazine also comes across as way more durable although the PMAG can take abuse much better from what I have seen on youtube. The HK magazine follower and spring set comes off as tough as the PMAG follower and spring set. For the money I would by PMAGs, but if you think plastic is crap then I would go HK despite the expense.
These are from my experiences, and your mileage may vary.