Another vote for, Use a Chronograph!
Look at it this way, the book says they reached max pressure with ABCD load, producing XXXX speed, in their rifle.
If you're not using the same primer and brass as the load manual it's not really the same load.
If you can't measure velocity, all we, or you can do is guesstimate.
Barnes bullets recommends their bullets be seated +-.050" off the lands for a running start, something to check.
Military brass is usually heavier and won't hold as much powder as commercial brass so dropping one grain may not be enough, I don't know!
You'd need a Chronograph to compare a single load between military and commercial brass. (I'll be checking 30-06 myself)
Lastly, your buddy's M855 ammo wasn't shooting monometal bullets which are usually longer than lead/steel core but you can't compare velocity anyway without a Chronograph.
