09-11-2018, 07:58 PM
I do not have any real world numbers, no chrony, but the Berger No. 1 reloading manual says that the Grendel yields +/- 17 fps change for each inch variance from 24" std barrel. I adjusted the JBM Calculator for my 25.56" (650mm) barrel and the trajectory seems to be close if not right on. I know that this is not what you asked for, but it might help weed out the chaff from the grain. In MY real world nothing is absolute and you will be getting good info from the guys; however, different barrels will return different results and there is where the confusion will come from. Good luck with your quest.