I don't know if this issue has been brought up already or not in these forums, but I just wanted to let you guys know what happened with my Smith and Wesson MP15-22.
Shortly after I received it, it had been functioning flawlessly. I then read an article in GUN Test Magazine where one user pointed out that the problem with the gun is that it can fire a round before the bolt is completely closed since there is no safety mechanism. So after prolonged shooting (more than 100 rounds) he noticed sparks and pieces of brass flying out from where the shells eject.
Shortly after I read this article, I had a similar problem with my gun. After firing a round, it did not eject the empty shell casing and I fired another shot with a partially chambered new bullet. This happened all so fast I did not even noticed that that the bolt did not even close. I pulled the trigger and it fired with the bolt half closed and the empty shell still in the chamber. Of course it sounded weird and I examined my gun and found out what happened. Luckily I did not get hurt, but my gun suffered some damage. The bolt was damaged a bit... not that bad because it is only a .22 cal, but significant enough to where I had to ship it back to Smith & Wesson. Thankfully the gun has a lifetime warranty and they replaced.

Overall, I thought this was a major flaw in the design of the gun and dangerous one at that. I was just wondering if anyone had similar problems or thoughts on this issue. Feel free to ask questions and post your own similar problems.