Yeah, depends on what you're breaking in.
For automatic pistols breaking in just means allowing the parts to wear together until they loosen up. Some manufactures say their guns require a break in period of so many rounds before the gun can be considered reliable. This doesn't take any effort, just refers to the first so many round fired.
But for a rifle used for hunting or competition, where accuracy is crucial, there is a process that you go through to "break in" the barrel. I've seen lot's of different techniques for doing that, but it involves a sequence of firing, cleaning, firing, cleaning, etc to properly prep the barrel for regular use. | 
When breaking in a firearm ......
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