Dahlgren sometimes provided tables like the one below to show how wild the range pattern would become if the powder IV were allowed to vary within the same lot of powder. The table shows very clearly the effect of gun IV variation due to powder variation.
This is why each and every batch of powder was tested at Dahlgren to ensure that each lot issued to the fleet would produce the same IV in a new gun with the same weight of projectile.
Occasionally someone finds one of these tables and incorrectly assumes that all lots of powder cause these variations in gun IV. That assumption is wrong: you cannot have these variations in powder because you would be shooting all over the ocean and never hit anything.
The only things that cause a variation in gun IV in the Fleet are changes in powder temperature and changes in weight of the projectile. You will never find in any USN textbook a variation in gun IV due to variations within the same lot of powder — Dahlgren made sure this could not happen by testing each and every lot before it was issued to the fleet.
Refer to OP 1100 — Range Tables for the 16″ HC Mk 13 Mod 0 for the full range table.
See also The USN Provided Information to the Officers and Men — Gene Slover’s commentary making the same point: no USN Naval Ordnance book records a gun IV variation from powder within the same lot, because Dahlgren tested every lot before fleet issue.
