But I kept it, and gave it a thorough break-in, removing copper and carbon every shot for twenty rounds, then every 5 shots for twenty, then every ten shots for forty - and every twenty rounds thereafter.
OK, so I'm trying to follow this logic- please explain what I'm missing or where I'm incorrect...
Shoot, clean the copper out of the imperfections in the leade. So, that leaves you where you started, or "where you started", less a little wear in the machining imperfections that exist. Right? It has to be one of the two, no other mechanism is acting on the barrel.
Seems logical you're not laying down copper jacket, only to be removing it over and over again...Like doing the same thing over and over, and expecting a different result.
Unless you're "removing", "wearing down", "smoothing-out", whatever you want to call it, the imperfections. Seems logical that's not only the case (friction, certainly), but also the objective.
Get rid of the imperfections. They're either hand-lapped out, or as Bart said, the shooter is simply making it the way it should have been in the first place.
I fail to see how
removing copper between shots, either extends barrel life, or improves accuracy. Copper fills the imperfections. Smooth leade...
Will the imperfections wear away faster with the copper removed? I'd agree probably so... but if you follow this logic, you're wasting barrel life as Gale M. says because you're just wearing out the barrel by altering the process that would take place anyway if just left alone.
Most barrels shoot better with a layer of copper fouling, which leaves me in the camp of "just shoot it" (not abuse it).
As to your Mosin-Nagant,
MANY things affect accuracy, and bore condition is only one of them. I'd bet I could put that action into an aftermarket stock, epoxy bed it, and shrink that group size significantly unless that bore is a sewer pipe- and if that's the case it shouldn't even be used as a basis of comparison. Tough enough to bring 100 year old rifles into a discussion comparing them to modern precision rifles.
Cut and re-crown the barrel, and free-float it along with bedding it, and it just might shoot 2-1/2"- 3" at 200 yards as both of mine do.