[Bart B.]

Fluting or turning down a finished barrel may change its bore and groove diameters under the flutes or turn-down area. Button rifled barrels' get bigger, hammer forged ones smaller. Cut rifled barrels may not change. It's best to flute or profile barrels before they're rifled. Use an air or star gauge to measure the bore before and afterwords to see the difference.

Any good, well made and stress relieved barrel will not change point of impact as it heats up as long as it's properly fit to a receiver having its face squared up with the chamber axis.