Factory rifles have been shot several times at the factory. I still break in factory barrels the same as rifles I build.
I clean the barrel thoroughly with a one piece stainless rod, bore brush, and solventthen a jag/patch withJB's, then wipe it out well with more solvent on patches. Dry it out, then shoot one round. I repeat this 10 times. Then shoot several 5 shot strings, cleaning between strings.
Most people never break in factory rifle barrels and they do just fine. I prefer to take every opportunity to ensure accuracy.