I purchased a mp 15 about 2 months ago and love it...however about 200 rounds in, the hammer pin has decided to walk out and get lost in a 100 acre field somewhere. Now on to my predicament. I contacted smith and wesson to see if it was possible to send a replacement pin and i would install it myself wich would save them time, money, and me a waiting period. I even offered to pay for the part if they were not able to comp me a pin(a 99 cent part by the way...but hard to come by in my area) i was replied to with. Our parts our factory fitted and you will need to send your rifle in. Here is the link to our return firearms label...expected turnaround 4-8 weeks . Are you kidding me i could install it in 4-8 minutes. Whats the deal with that i would rather not buy a 3rd party part for fear of loosing my warranty but i may have to...because im not waiting that long for something that small.