MFT mag holds bolt open on empty ONLY if I shoot slowly. Why?

[Gatehouse]

Hmm, I have never had a problem with the MFT LAR mags in 2 MP15's, 2 Norinco AR's, 2 NEA AR's and one Tavor. I have about 5 or 20 of the MFT mags. I've been using them since last summer and all through the fall and winter so variable weather conditions.

I'm wondering if you got a bad batch or something? Or they changed something?

 

[LAV]

The saga might be over. I went to the range with 10 mags. It was -15C. I used Federal bulk 55g. 8 magazines worked fine inluding 3 CPD, 1 Hera 5/30 and 4 MFT mags. Two mags failed, both MFT. I disassembled them. Shot them with and without extensions. On closer inspection, both of the followers of these two mags have a little bit of plastic material missing. It as if something was forced/pushed through and tore off some of the plastic material from the back/top part of the follower. I will post a pic if I figure out how to. That is the only thing that I found different from the two mags that failed and all the other ones I tried.