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?

Quoted: I have been trying several different types of factory 147gr  9mm ammo out of my 7.5inch barreled AR-15 and most of it is going supersonic which is not good since I am in the process of adding a suppressor to the gun. What are you considering sonic?  1050 fps tops for safe noise free bullet flight down range. So far most of the top end hollow point ammo is shooting around 1100 to 1150fps.   Sounds like 115 and 124gr stuff I was wondering What FPS most people are  getting with anything from a 6 to 16" AR-15 barrels 9mm with 147gr loads? I handload all my 147gr 9x19 ammo, cost way tooo much to buy factory... I stick to about 1000 fps over the chrono here. I have (1000) 147gr RN Berrys coming, I may  bump them to 1025-1050 fps if I can get away with it. They only 147gr factory Hollow point load I have treid to stay at 1000fps was winchester 147gr  silvertips. I bought a box of 147gr Silver Tip at Wally World one night to have amo to demo suppressor to brother in-law,  $20/50ct box.... OUCH !   Ended up wasting the rest in the M11 with AWC Mk9, talk about quiet.. I am wondering if it is just this gun or my chrograph is missing up? Stay back about 10-15 ft with pistol when chrono, so  timer not get fooled by muzzle blast trash tripping the sensors. Shoot straight across... I have reference lines on mine to center the shot with.

I was looking and it sounds like the barrel has to be around 3" to keep 9mm loads subsonic.  

147grain round nose should be subsonic in your weapon.