He prob'ly got it. Because it only happened on the first round in several clips , it would indicate a part that did not remain in the same place during the next few shots. Ie , follower , follower arm , grooves in the reciever that the follower rides in , etc. Could also be the mainspring if it was too long , but that's a rare thing for it to be just a hair too long and work for the rest of the shots.
Chris