I have been trying several different types of factory 147gr 9mm ammo out of my 7.5inch barreled Ar15 and most of it is going supersonic which is not good since I am in the process of adding a suppressor to the gun. So far most of the top end hollow point ammo is shooting around 1100 to 1150fps. I was wondering What FPS most people are getting with anything from a 6 to 16" ar 15 barrels 9mm with 147gr loads? They only 147gr factory Hollow point load I have treid to stay at 1000fps was winchester 147gr silvertips. I am wondering if it is just this gun or my chrograph is missing up?