I went to the range yesterday. Had a great day shooting my new M&P 9mm and working with my new Super Tuck and Serpa holsters. Put 500 rounds through the pistol with no issues at all. I only took the M&P 9mm and it's holsters. I wanted to practice and drill with only it. A full focus range session so to speak on one weapon and two holster systems. Using my own reloads, being the ammo I will carry in this pistol. I was running 124gn XTP's over 5.9gn of Power Pistol, Fed primers with new Winchester brass I got for dirt cheap. I got home and the wife and I decided to go to a local street Art Festival and enjoy some street food and people watching. I told the wife. "let me clean up the M&P 9mm real quick" Then I changed my mind about cleaning it up. I told her "never mind it's been running great, it should be fine". I'll load it up and we will be off. I put one round in a empty mag to chamber one and BANG she went off. My view from my desk. The pistol fired and locked the slide back. I dropped the mag and rolled the pistol over to inspect. And found the striker poking out the breech. I was then so thankful that I had not loaded a full mag. That could have been ugly. Real Ugly!!! The round went through my monitor, inner window trim, king studs, outer window trim and lodged in one of my pecan trees 6' outside my window about 20' off the ground. Once I had figured out the trajectory of the bullet and it was proven secure. I detail stripped the pistol. Focusing hard on the striker and striker channel I found very heavy brass shavings packed in the striker channel. I then went through the new brass I shot and inspected each piece. I found a extractor wear mark on almost all of it. I then pulled the extractor and sure enough it had a burr that matched the mark on the brass. The little burr cleaned right up. I refitted it and took the pistol to the range early this morning. It did great. Came home and striped it back down. No big brass flakes in the striker channel and no marks on the 100 rounds of brass I fired this am. Now that the pistol is fixed and the malfunction understood. I have to fix myself. I have always chambered and dry fired my weapons in this room at my desk with them pointed at the floor or my wrist on the edge of the desk surface with the pistol pointed just like it was with this AD. No more desk top loading or dry firing! Yeah the monitor, house frame, trim and tree did there job. I didn't do mine. From now on the weapon will always be pointed at the floor. With a crawl space, dirt and foundation stone to stop the bullet. In slightly over 40 years of shooting and handling guns. This is my first AD and I hope my last. I really freaked the wife out big time. I'm ok and nobody else was hurt or even close to being hurt. My ears and eye's are fine. I think I will leave the bullet hole in the trim to remind me of my mistake. Be careful folks.