A friend and I were having a little shootout on his back porch last night...When his XDs .45 started spitting out multiple round bursts. First it was a series of 2 round bursts. After about half a dozen 2 round bursts, it spit out a 3 round burst. It did this a few times, then finally spit out the 4 round burst. Anyone have any idea what could be going wrong? Is it possible that he could be accidentally bump firing some how with the way he's holding the gun and/or pulling the trigger? His grip is the standard thumbs forward grip. Anyway, it's in the shop getting checked out. Just wondered if anyone has heard of such behavior from the XDs or any semi-auto for that matter.