I had a pound of IMR4350 that needed using up, so I decided to work up a load for my 7mm-08 using swift scirocco's. I decided to do a ladder test, starting with 44gr. and working up to 46.2gr in increments of .2 grains. Groups really started tighten up near the end of the test. I went home and loaded up a bunch of rounds then headed back to the range. It seems that every time I go to the rifle range there's a million people there and I always feel rushed. I rarely get to shoot the way I want to, let alone have the opportunity to set up the chronograph. When I got back I was happy to have the range all to myself. I fired once, made the sight adjustment and shot 3 rounds. I was very happy with group. Swift had 46gr at 2721ft/sec as their max load. Mine were not quite up to that mark with 2653, 2667, and 2674.

There are too many variables that effect a bullets velocity to hold a posted FPS as gospel.
Powder lot number
primer lot number
true bullet weight
bullet diameter
bore size
how the chamber was cut and to who's standards
bore cleanliness
air pressure
air,powder,barrel temperature
wind
accuracy of chronograph/sun placement/battery power.
Most of the powders tested are using freshly made powders and fired in a universal receiver type firearm in an inside range in ideal conditions using a barrel with an untold number of rounds fired through it.
While you probably will be within a few hundred feet of posted FPS.

Id call it darn close

A 50 t0 70 fps reduction is very close I have seen book velocities and actual velocities of over 200fps different .

Barrel length as well.

...and we haven't even ventured into chronograph accuracy and precision....

I find with Chrono's that consistency of SD and Range or ES is more important than velocity.

Technique is as important and the instrument.

In many cases we tend to overthink such things. I guess that's part of the game, but the older I get the less I care about 100 FPS, as long as it shoots a decent group, and those half inch groups have become less important, and three shot groups get me home faster..

What a relief!