When a cartridge is fired in the chamber of a rifle
it sets off an oscillation in the barrel.. In the WHOLE
barrel, chamber to muzzle... As the bullet travels down
the barrel, the oscillation increases in frequency..
It can be viewed much like a electrical sign wave on an
oscilliscope. With the baseline, and the active signal
passing above and below the baseline.. As the bullet
travels down the barrel, the wavelength decreases, which
increases the frequency of the oscillation, until the bullet
leaves the muzzle.. Like the whipsaw effect...
This whipsaw effect can be altered by the thickness and
taper of the barrel, the method of its bedding, (full bedding,
post bedding, or free floating).. And the speed of the bullet..
This effect is universal, to ALL gunbarrels..
For optimum consistancy, (optimum accuracy) the bullet
will leave the muzzle exactly at the moment when the
oscillation passes thru the baseline...
There are other factors in this oscillation as well, density of
the steel, lay of the grain during the forging process, temperature..
No two barrels will be identicle, even from the same lot of steel
and the same forge..
Common practice is to adjust your loads to the barrel, which
can control this effect.. rather than the barrel to the loading..
It'll make a tremendous difference, when you find that sweet
loading, that matches the barrel...

Good luck
RC