Roper, I did see the differance, but it got worse the closer I got to the max (25.3).
I did missread the test barrel length, I was seeing 20" not 24". Oops! Thanks for the heads up.
That does make me feel a bit better, but I am still over 300 fps slow at 25.3 gr. The SD for all loads was higher than 20. Lowest ES was 51 with a 23.6 gr load (SD 23) and velocity at 2783 fps.
I have a DPMS with a 20" barrel, I'm gonna chrony these same loads through that gun. See what happens. It appears that barrel lenght is the culprit, not my chronograph. Thanks guys.