This is a new gun. Well now it has 360 rounds fired through it. I thought it just needed broke in till I noticed some marks on my casings. After noticing these marks I went and shot a 30 round mag through it and paid more attention to what was going on. It doesnt start failing to chamber till it blows the oil out of the chamber. The first time I shot it I got like 37 rounds down range before failure. Today it was like 5. These scratches are on all the casings even when the gun is dripping oil. Some are worse than others especially the ones that dont chamber all the way. The scratches start on the shell about 3/8" down from the shoulder and continue for about 1/4". They stop almost exactly half way between the shoulder and the base of the shell. When the round is in the chamber the scratches go from 12clock to 3:30 maybe 4clock. Its hard to see that area of the chamber since I cant find my handy little mirror but I think I see a little "ridge" in there... It seems that the rounds coming out of the left side of the magazine are the ones that stick. Out of the 30 rounds I really paid attention to what was happening. 6 of them failed to fully chamber. All from the left side of the mag. I only tested on one mag out of 4. But failures are consistent in all the mags.When the gun is cool I might get 10-15 rounds down range. Sometimes Ill get 5-7 rounds down range sometimes only 3. The warmer the gun the more failures happen.Sometimes when I pull the trigger the bolt slams the rest of the way shut and sometimes it doesnt. Its a S&W so its under warranty but I dont know how long they will keep it and if its as simple as I think it is Ill just smooth it out myself. This is my first AR so I dont know if this behavior is normal. It doesnt seem that way. My new 1911 leaves very similar marks on the brass but it doesnt jam every 3 shots. Ive never had this much trouble out of a gun. New or used... What do you guys think? Thank you for reading my mile long post!