Frank,
My programs say 4.4, 4.45 and 4.4 moa.
The two that give drop say 18.47" and 18.65".
Not sure what Darryl used, but it's quite different.
I used Oehlers Ballistic Explorer, Load From a Disk and Horus Vision's ATRAG (SMOA) respectively. All at 35 deg, 300 ft elevation, 3340 fps and .55 BC.
Either your 100 zero is .5 moa high, the BC is actually higher, the velocity is actually higher, a combination of the above three or the G1 drag curve doesn't accuratly model the bullets trajectory exactly.
Shooting at longer range should help to clarify things better.
Good luck.