Incorrect bolts? - XS Sight Systems Shotrail Shotgun Sights

The bolts included with the rail do not appear to be the correct thread pitch for my newly purchased 870. I do not have the tools to test, but they were difficult to thread in and show signs of damage at their ends that indicate cross threading. I got them in finally, but am concerned they may not hold over time. For this price, there should not be an issue like this.