I have loaded up a trial batch today of 55gr BT-fmj Hornady bullets with LC cases, cci sm primers and 21.7 gr or IMR 3031 @ 2.200 C.O.L. All the books and reference I can find are saying these should be pushing 27-3000 fps depending on what reference you use. I ran some through my Chrony today and the fastest I had was 2417 and slow or around 2350. I was using an older 16" AR upper I have that I know is pretty worn but functions ok. All the rounds cycled ok and seemed to have plenty of pressure. Why am I getting such difference from spec to chrony ?? The cases all look good also .