Barrel break in is only beneficial to precision after market barrels. Factory barrels aren't smooth enough to benefit from a break in regimen. The point of the break in exercise isn't to improve accuracy, as the precision barrel does not become more accurate with use. The point is to reduce fouling by smoothing out the very fine marks left from the chamber reamer; cutting a chamber is seldom done by the barrel manufacturer. The chamber reamer cuts across the grain of the steel and leaves small, hair like, protrusions of metal. A proper break procedure removes these hairs resulting in a smooth finish.
When a cartridge is fired, copper is cut from the bullet as the lands displace bullet metal from its bearing surface, and this stripped copper is then suspended as a plasma in the super heated gases which propel the bullet. This copper is deposited along the bore after the passage of the bullet as fouling. A rough chamber throat adds to the volume of copper that is suspended in the plasma. To visualize what happens during the break in, consider a piece of steel that you've cut with a hacksaw, you'll note the edge of the cut has hair like slivers of metal forming a ragged edge. If you heat those slivers of metal with a cutting torch until they glow red, then give them a rub with a steel brush, they break off leaving a smooth edge, much smoother than say touching the edge up on a grinder. That's your break in. I suspect that in most cases, 20-25 rounds is sufficient to accomplish this, where the first 5 are shoot one clean one, followed by a few groups of 3 shots with cleaning between each group, then a couple of groups of 5. Some folks soak the bore in Kroil after each cleaning to burnish the bore and fill the pores of the bore surface.
Does your barrel benefit from a break in regimen? That depends on how important you think it is to remove copper fouling from your bore. Some folks see fouling as a benefit while others prefer to keep their bore as close to bare steel as possible.
