Every barrel I know of whips and wiggles at the same frequencies and amounts for every round fired. They don't heat up enough to change their resonant and harmonic frequencies.
http://www.varmintal.com/amode.htm
Every bullet of a given type I know of is not exactly the same shape nor perfectly balanced nor leaves at exactly the same speed. Nor is the air they go through constantly stable for each one fired.
If these weren't true, then a test made with bullets selected for perfect balance shot from a rifle clamped in a machine rest shoot several 10-shot groups well under 1.5 inch at 600 yards. And a 40-shot group under 2 inches. Each group started with the barrel cool and shots fired once every 20 to 30 seconds. All done at dawn when the air is most stable.
Commercial factory barrels walk shot impact as the heat up from poor fit to receivers. Refit them to a squared up receiver face and that won't happen. If they're properly stress relieved.
Every rifle fired will once in a great while shoot a very tiny group. Even a few record setting benchrest rifles do that once in their life. A lot fewer do it twice.