It's confirmed. The Check-Mate mags that came original with the gun are a PITA as far as feeding/retaining the top round (the top round can, quite literally, fall out). The top round can nose up in dramatic fashion if inserted energetically, and will nose dive on the feed ramp on occasion. Once the top round is chambered they work, but when a partially loaded mag is ejected a loose round often follows. The front ramp style Metalform mags I got from their promotion are flawless. YMMV.