"So I bought 7 of these mags a few months ago as extra magazines and also to replace the crappy ones that I initially received with my first gun, and I was a little worried about the black "lip" that they have on the top of the magazine where the bullets would go in IRL. Thankfully, I have had no trouble with getting these magazines in/out of my rifle, and I didn't have to do any modifications on the magazines or the rifle itself. (I have a full-metal DBOYS M4 AEG from a different website.)
I tested out the capacity on one of the mags by loading it and unloading it 3 times in a row, and the results were that it held 123 the first time, 116 the second, and 101 the third time. I've heard that it's not good to fully load your magazines or keep them full for extended periods of time as it can damage the spring and I really hope that wasn't what was going on with the decreasing numbers...
Anyway, after that I loaded the other 6 magazines up once each and they held 91, 101, 115, 114, 94, and 112 rounds each. That averages out to a little under 110 bbs per magazine, which I think is more than enough considering the real thing only holds 30 5.56 NATO/.223 rounds, even though these airsoft versions are advertised to hold 120bbs.
Another 'test' that I performed on these was to find out if it had a realistic weight. I didn't actually have a scale on hand when I performed the test, so I just estimated by how they felt in my hands. I took a real AR-15 magazine as well as one of these airsoft magazines and proceeded to load/unload them for each part. I found that when both magazines were unloaded the airsoft mag felt a little bit heavier, but when they were both loaded the airsoft one was a little bit lighter. Go figure.
I initially bought these magazines because they are metal and gray in color like the real steel ones, instead of a matte black like most airsoft m4/m16 mags are. However, these mags do have a black "lip" like I stated earlier, but that doesn't really matter because they're going to be inside your gun or your pouches anyway. The paint scratches and rubs off on other metal surfaces like your mag well after extended use, but I think that just gives them character and adds to the realism anyway.
They have a rough texture to them which surprised me a little when I first got the mags. I really had to stuff them into my mag pouch to get 2 of them to fit in each pocket and yank on them while working the magazine side-to-side in the pockets to get them out at first, (I have the Triple M4 / G36 MOLLE Ready Magazine Pouch by Condor / Phantom - Tan pouch from this site by the way), but after leaving them in the pouch for a week or two and periodically working them out of the pouch and putting them back in at different angles to stretch it out, they fit alright now. The problem was probably caused by a combination of the texture of the magazines that made them sort of grip each other, the lips on the mags stretching the pouch more, and the already tight pockets of the pouch.
I've dropped these things a few times and they took it like a champ, they barely wobble at all in the mag well to a point where it doesn't even matter, and they all feed efficiently too.
Pros:
Durable METAL
Extremely minimal wobble
Feeds well
Mostly realistic appearance and weight
Sufficient capacity
Excellent performance for the price
Paint rubs/scratches (can be a con)
Cons:
Paint rubs/scratches (can be a pro)
Sorry for the long review, but I wanted to make sure that I put down every detail that I could think of. All in all, if you're looking for a good quality magazine that's not going to break the bank, this is the one to buy.