re: Official AR-15 thread

That's the front takedown pivot spring and detent. Forward to 3:58 in that video for a pretty easy way to not frick it up. I use that method, but I just push the detent in with my finger nail and hold it while sliding the allen wrench over it. Have never had the need to use the needlenose and pick as he does. I recommend setting up a grocery bag, pillow, or something in front of it though to catch the detent in case it does fly out.