Some barrels produce slower FPS than other of the same brand and length.
IMO don't worry about the fact your load is slower than the book says.
At ethical ranges the deer will never know the differance.
With a 200 yd zero your "slow " load will only be 1.2" or less lower at 300 yds.
Whats the big differance ?? DEAD IS DEAD !!

Johnch