Unexpected velocity difference from manual

[XLR308]

With my first ladder through a new 6.5x47 barrel I just now went back and compared my velocity to what is published in the Berger manual.
The bullets are not the same but very close.
Data from the manual is for the Berger 120gr match BT target and i was using the Nosler 123CC comparing both with Varget.
Barrel lengths are the same at 24", I ran my ladder from 36 to 37.8 grains with a CBTO of 2.1115 and .010" jump.
Now the part that surprised me between 37.4 and 37.8 my velocity peaked and then flattened out on the 37.8 load but my recorded velocity was 123fps faster than book max with less powder.
Recorded velocity for the top four charges were
37.2gr. 2892fps
37.4 2900
37.6 2950
37.8 2922
I've usually ended up pretty close to book velocities but mostly slightly under not over by such a big margin.
Those of you that have far more experience with the 6.5x47 than me do these velocities seem to be the norm ?

 

[wilson1911]

47 reamers are usually pretty tight. At least all of mine have been. Also, if your just to or in the throat it will create more pressure.

 

[XLR308]

47 reamers are usually pretty tight. At least all of mine have been. Also, if your just to or in the throat it will create more pressure.

I'm only .010" off but was still surprised by the velocity difference.
I shot a five shot group the next time out with the 37.6 load to see how it would hold up.
Pic is 5 rounds at 100 yards with cold bore shot included.

 

[Lowlight]

next jug of powder will be different, the jug you get after that will probably change again,

these are reference numbers, a guide, not a fact written in stone.

 

[XLR308]

next jug of powder will be different, the jug you get after that will probably change again,

these are reference numbers, a guide, not a fact written in stone.

That's an excellent point, these loads are from the 8 pound container I'm currently on and the oldest container of Varget I have.
I may open one of the newer ones from a different lot just to see what the difference will be before I actually need them.
I know the Berger data is fairly conservative from comparing to much of the data I have found on here and other sites so really haven't found max in my barrel.
Given the velocity I'm seeing so far with this lot of powder in the new Schnieder barrel I probably won't be running much higher.
Next time out I need to shoot a 10 or 20 shot group at 600 with the same load.
If it holds up as well I will just load up 100 for my plinking loads.