Picher, every barrel gets longer and thicker when it heats up. So does any other round bar made of steel.
The reason why most factory barrels "warp" when they're hot is they're not fit to receivers whose face is squared up with the barrel tenon threads. When the barrel and receiver expands from heat, more pressure's applied at the hard contact point and that makes the barrel bend in that axis.
I've had three factory barrels that changed point of impact when they heated up but quit after some 'smithing. The receiver face was squared off and set back about .005" then a .005" thick shim washer was put between the barrel and receiver so it would clock in correctly for the extractor to fit the cutout in it. No more walking shot impact as the barrel heated up. Any competant 'smith can do this to most factory bolt action rifles.
Arsenals testing 30 caliber and 7.62 match ammo shoot a couple hundred shots per group; each about 20 to 30 seconds apart. Those test barrels get very hot yet still shoot good lots of ammo into 1 MOA at 600 yards; would be under 1/3 MOA at 100 yards.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master