I've broken in barrels in -20F. I step outside the door, shoot into a stump in the back yard, step back in the house and strip the bore down to bare steel. If you can shoot in your yard, you can break a barrel in regardless of outdoor temperature - extreme hot or cold. My barrel is more or less room temperature no matter the extreme variation in outdoor temps because the barrel and cleaning solvent are in a temperature controlled setting 99% of the time. Of course you may not be able to shoot at your residence, then you do have to consider creature comfort, or look for a relative or buddy located where you can set up and shoot 10 times without being reported to the local Police Department.