Sir Charles,
I believe what could have been causing the issue was with the chronograph 6 feet from the muzzle and using (Lite) lower velocity loads, the escaping powder gasses from the muzzle were traveling faster than the shot itself and thus giving higher readings.
My only experience with chronographs (I have 2 of them) has been with pistols and rifles and none with shotguns. THese days I typically use my Chrony since it is easier to set up than my Ohler and a side by side comparison has indicated that the Chrony is just about as accurate.
For my tests I set the front of the Chrony about 10 feet in front of the muzzle and that has worked very well.
Getting back to .44 Henry Ballistics in the .44-40, 10 or so years ago I removed the powder from an original 200 gr Henry Flat cartridge which weighed 28 grs and was FFFG granulation. I placed the charge in a .44-40 case and compressed it the same amount of compression used in the .44 Henry case.
I used a 155 Federal Magnum pistol primer to ignite the powder which pushed the 200 gr cast bullet to a 1,133 f.p.s. Chrony reading.
The Winchester 1875 Catalog indicated a velocity of the .44 Henry to be 1,125 f.p.s. so 1,133 f.p.s. is pretty darn close.
I decided to use the slightly hotter primer since there was a greater amount of priming compound in thr Henry .44 RF ctg.
Furthert testing of 28 grs by weight of Goex and Kik FFFG powders gave velocities in the same range. I tried both the Fed 155 magnum and CCI 300 std pistol primer and the velocity difference was very small...less than 20 f.p.s.
The difference in velocity between mine and FCK's is that perhaps he was using FFG instead of the FFFG I was using and his rifle has a shorter barrel.
w44wcf