Just a heads-up. I bought six of the 17 round Glock mags (newly manufactured) about three months ago.

The spring tension was noticeably weaker than what you'll find in factory springs, but I didn't really care (at the time). But now, after about  24 cycles of filling (downloading by one round) and shooting, the mags will not reliably/consistently lock the slide open after the last round has been fired.

I carry 22 loaded mags when I go to the range to practice, and usually go twice a week. (Plus I make additional trips to the range with students.) My typical "loadout" includes three of the Magpuls and 19 Glock factory mags. Only the Magpuls cause the slide lock problem, so I'm pretty confident (even if I weren't a State Police concealed handgun instructor) that the problem is either with the springs or the followers that Magpul is using.

This wouldn't ordinarily be a big issue -- it's always good practice to deal with stoppages/malfunctions. But it's not good to have this happening when we're working with students on marksmanship fundamentals.

My call to Magpul tech support didn't yield anything beyond (a) confirming that these mags are not built with Glock factory springs or with Wolff springs, and (b) a suggestion that I return the mags for inspection (with the possibility of having them replaced).

I declined, since the replacement mags (if they were to be provided) would be identical to what I have (i.e. there have been no changes in the mag followers or springs since I bought mine). So it's cheaper/easier for me to just toss them out instead of boxing them up and shipping them to Magpul (and then go through more beta testing with replacement mags, if replacements were to be provided).

Not trying to throw any rocks at Magpul. The tech support guy was very polite. But just wanted a offer a note of caution for anyone that might be thinking of using these mags for carry or for competition. I'd stick with Glock factory mags for those uses.

I've not noticed weaker springs- rounds 15 16 17 are tough to load on mine - but I have noticed the follower does seem to get hung up at the top, sometimes causing a skip over when there are two or three rounds to go. not every time, but often enough I'll use them for the range, but not carry or competition.

I wonder if you followers are getting hung up in the same area. I only have two but I've been running through 3-4 cycles a week for 4-6 weeks at the range with plain Jane RTP ammo.