Yep, two different 30-06 rifles, both 24", but one always gave nearly a hundred feet a second more than the other, with any load.
58 grains of 4350 and 165 Hornady bullet, one rifle gave 2778, while the other averaged 2696. Mild loads.
With the slower rifle, 60 grains of Norma 204 averaged 2912, which still was a very normal load.
At the time I was doing this, I noticed one of the major reloading books showed 54 grains of 4350 as a maximum in the 30-06 with a 180 grain bullet, and giving a velocity of the usual 2700 fps.
I duplicated their "maximum" load and it gave me 2436 fps!