When I've chronographed factory 123 grain A-Max it averaged 2464 FPS out of a Brownell's 18" Grendel II chamber (Satern/Liberty barrel) 1:8 twist on a 70 degree day. The Hornady 123 grain SST Factory averaged 2490 the same day with Magneto Speed Chronograph.
Here is a picture of the velocity curve LRRPF52 has posted from the Grendel handbooks.
Here is a picture of the velocity curve LRRPF52 has posted from the Grendel handbooks.