Here is what Bob Londrigan says:
Keep the gun lubed up well during the entire test
Clean the gun after the first 500 rounds or so or if it gets so dirty that it slows the slide down. Otherwise, don’t worry about the buildup of dirt. The powder residue mixed with oil makes a good lapping compound.
Do not try and speed up the break-in period by polishing, filing, or using any type of abrasive compound. You just might end up with a sloppy fit by the time you finish.
If you are using new magazines, use just one or two for the initial break-in. This will speed up breaking-in the magazines and it will limit the number of variables if you have problems.
Remember to check the zero on your gun after you have it sighted in. It is possible for your zero to change a little as the parts take their final position.
Don’t heat your gun up so much that it could cause damage.
If followed, the break-in procedure I have described will result in a gun that is clearanced enough to function reliably without losing any of its accuracy.