I'm new to AR's though not to guns and shooting in general. That being said I now have an M&P-15. I bought it just before the craziness began last month along with a Bushmaster complete upper in a different caliber as a Christmas present for myself. I would like to replace the original take down pins with the quick release type as it should be quicker and less trouble using the QR pins when I want to swap uppers on the gun or clean it. However, I can't figure out how to remove the old pins. I push the pins through until the upper tilts out, but the pins simply stop and lock when they become flush with the inside of the lower receiver. I would suspect there is something in the pin's grove that prevents the pin from coming out but can't figure out where/what it is. Is there a "trick" to removing a pin completely? Any help would be appreciated!