Instead of putting my facts on the sight so other's can write it off as opinion let me ask you this!
What is the hardness of your average steel centerfire rifle barrel?
What is the average hardness of copper alloys used to jacket lead bullets?
Do you have to break in the chamber by expanding 70/30 brass cases into it? Oh and so you know the 70% is copper the 30% is zinc.
What causes most barrels to be shot out? Is it rifling wear to the lands or groves? Is it throat and crown erosion?
What causes throats to erode and crowns to erode?
If you look at the tools used to make a barrel and then look at what a bullet is made from it is a fools folly to think you can break in a barrel by passing a copper alloy lead slug down the bore. The abrasion comes from powder and heat and pressure of the combustion is what does a barrel in not frictional mechanical wear. That is also why you can look at a Savage barrel for instance after 1000 rounds have gone down it and if you ignore the throat and crown it is still looks nasty and rough nothing has been worn down. If you look at Remingtons pre-CHF you will see all kinds of artifacts that have been their since the barrel was made even 5000 rounds later. Last but not least if break in was a real thing and not magic nonsense then taking a 1/4 inch off both ends and rechambering and recrowning would not work as consistently as it does to restore 90% of the original barrels accuracy as often as it does (not talking about BR levels of accuracy for the record)! The US Army requires or required 20K rounds of accurate fire on the
