Bill, I am not familiar witht he book you cited, so at the risk of preaching to the choir.....
Does the data book spec the distance from the muzzle the readings were taken, so as to duplicate with your set-up?
As an example I think I recall in the transition between two of the Lyman's manuals they went from 15' to 3' from the muzzle.....English specs are even further out?
Are you using a light card over the shot that might be blowing through ahead of the shot?
I ran a hypothetical ounce of #7 at "1100fps" (3ft from muzzle as per SAMMI?)...reportedly leaves the muzzle at 1150 fps and is down to 950 at 10yds.
While our chronys are not he same type of instrument used for the actual tests, I usually get very similar readings to the load data.
It would also not be unheard of for the data to be off, can you cross reference to a same or similar load from another source?
Best,
Mark
