all you have to do is trip the button on the bottom left side of the mag to bypass this-conversely if you stick a 760-7600 mag in a 742, 740, or 7400 she puts the round into the chamber RIGHT NOW- apparently you're SUPPOSED TO PUSSY FOOT the chambering of rounds in this gun- put the round in the chamber through the ejection port,then trip the bolt release( the hold open device) and EASE THE BOLT FORWARD- SO SAYS THE MANUAL, then on safe, eject the mag , and fill the mag, and then put it back in the gun- I'VE NEVER DONE IT THAT WAY- just like the m14, i chamber right off the mag by tripping the bolt rlease and letting it fly