I have a bunch of these, both 15 and 17 round 9mm magazines. Initially, there were some that were not dropping free when empty, but they have "broken in" and now do drop free from multiple pistols. I've been in the habit of always taking a Korean mag along when I take a Glock out for some practice, which is pretty often.
Loading the 15-round magazines, along with a couple of Glock factory magazines, I noticed that Korean magazines were noticeably easier to load. Although I haven't used the Korean magazines all that much, the springs had compressed a bit, and were just a little bit longer than the mag tube. To the credit of the Koreans, the mags actually never failed. Regardless, I replaced the Korean springs with Wolff extra power springs, and the Korean magazines soldier on.
The KCI spring wire diameter is 0.045". The Glock magazine spring wire diameter is 0.051". The Wolff magazine spring wire diameter is 0.048", but is obviously a much longer spring. It doesn't seem like a lot, but I think you can see that the Korean spring is smaller.
The 17-round magazines don't seem to have this problem, or at least it hasn't manifested yet.
The Korean magazines are significantly cheaper than Glock factory magazines, but consider the added expense of the replacement spring before you buy. Centerfire Systems sells the Korean mags for $8 and $13 each, and I wouldn't pay very much more than that. Brownells sells 3-packs of Wolff magazine springs for $18, IIRC.
And yes, I'm sure that that is the right Wolff spring for that magazine, and yes, I can still get 15 rounds into that magazine.
Lancer AWM AR-15 Magazine
I've been trying out one of the opaque black 30-round magazines for a little while. I was just about to add it to my SHTF stash. This weekend I was shooting one my carbines, and when I inserted the AWM magazine into the rifle, I noticed that a round popped loose into the action. Although it struck me as odd, I cleared it, and continued on. I came home, loaded the magazine back up, and tried that a few more times. I tried downloading the magazine 1, 2, and 3 rounds. When inserting the magazine "with vigor," but not abusively hard, I was able to duplicate the failure over and over again. Dropping the magazine from two and a half to three feet onto a carpeted floor will also release a round about half the time.
I think I bought 3 of these. I don't think I'll buy any more.
It would seem that I am not alone. Did some searching, and I found a m4carbine.net member, G19A3, had reported the following.
Although I cannot recommend Lancers either, I loved the translucency, but found that they tend to "waterfountain" a round or three when slapped in authoritatively on a bolt-locked-back condition. I experienced this with 30rd Lancer L5's and the later 20rd AWM's. I roll only Colt or OKay USGI 20rd & 30rd aluminum mags now. I'm still hoping one day for a translucent mag that doesn't do this. Someone indicated on another thread they have tested the new HK translucent mags for this and they are GTG in that respect, but I haven't tried them yet. I understand AUG mags do this too in a bolt-locked-back condition. Must be something about the polymer to make a translucent mag, even with metal reinforced lips like the Lancers.
The last couple of times I took this magazine out, I had bolt-over-base malfunctions. This is with two different brands of ammunition. Never had this happen before with this rifle.
I had it happen twice within about 12 rounds with Wolf Gold .223 Remington, 55 grain FMJ. I unloaded the magazine, and loaded the remaining rounds into another magazine, and continued shooting without issue. Went through 4 other different magazines (that day), without issue. It's hard to draw any conclusion, other than that the CAA magazine is the problem.
The CAA MAG17 also will not firmly lock into the ACR. The notch for the magazine catch is a little small, and I guess the ACR mag catch is a little larger than that of an AR-15 or M-16/M4.
Fortunately, I only bought one of these. I like the features of the MAG17, but I'd rather have magazines that don't induce malfunctions.