I recently purchased a M&P 15 Sport. I have had some problems with the gun jamming. I am using the stock pmag and bushmaster 30 round magazines that came with the gun. I am shooting Remington PMC factory .223 ammo purchased from Walmart. I have fired the gun about 80 -100 times. If the bolt and receiver are not well lubricated with Breakfree CLP or Rem oil (or other such lubricant), the gun will jam. Specifically, the gun will lift the cartridge from the magazine but will not push it into the chamber. The cartridge will get caught between the bolt and the chamber. The cartridge case will be well dented near the shoulder so bad the cartridge will have to be discarded. This problem happened about 1 in 3 rounds when the gun was first fired. It now happens about 1 in 8 times. Several shooters of ARs at my gun club have observed this problem with my rifle and tell me the gun just needs to be shot in rather than sent back to Smith and Wesson for repair. The fired cartridge cases have observable scratches on the case necks and the case bodies. I am interested in getting readers opinions and advice. Also, what 3 shot groups are reasonable at 100 yards? Thanks in advance.