What You Need To Know About The Barrel Break-In Process
by Grant Ubl

Mystery and misconception surrounds the barrel break-in process. Is it necessary? How long-winded should this process be? What are the benefits? All are viable questions.

Before we get into various break-in procedures, let’s look at how barrels are manufactured and what shooters face when approaching a virgin barrel. Barrels are manufactured using several different processes to put the rifling into the bore. The processes selected and the finishing or final-lapping technique used will determine interior barrel smoothness. Here, we’ll assume that all barrels in this discussion have the exact same interior dimensions. Always keep in mind the barrel production process might leave minuscule marks in the bore that are 90 degrees to bullet travel, which will affect the collection of fouling.

More:
https://www.ssusa.org/articles/2017/12/21/what-you-need-to-know-about-the-barrel-break-in-process/