Excerpt from “Breaking In a Barrel” by Lee Shaver (muzzle and breech loader gunsmith extraordinaire) :
Several years ago, I developed a process for breaking-in barrels for lead
bullet use that eliminated the afternoon of shooting and cleaning with
jacketed bullet. It began because I would occasionally have to get bad
leading out of a barrel for a customer, and when you charge what a
gunsmith must charge to stay in business you don’t want to spend an
afternoon scrubbing the lead out of a customer’s gun. And I’m sure the
customer would rather not pay for said services.
What I learned was that when scrubbing lead out of a barrel, I could run
a tight oily patch through a few times and then take the patch off the
jag. I would then unroll a little 0000 steel wool and cut a piece the size
of the patch. Place that over the patch and then run it all through
together. (The proper fit is when you have to bump the rod a few times
with the palm of your hand to get it started in the bore.) When you
shove that steel wool over a patch through the bore of a badly leaded
barrel, it may sound like paper tearing as the lead is ripped out of the
barrel in a pass or two. I can clean the lead out of the worst barrel in
about ten or fifteen minutes that way, and an average leaded barrel will
be clean in a few strokes.
After using this technique for a while, I began to notice that the rifles
that I was de-leading that way seemed to lead less afterwards, which
got me to thinking. We use fine steel wool on the outside of old guns all
the time to do some cleaning or spot rust removal, and it does not
damage the surface of the steel. It just scrubs it. Which lead me to
consider the fact that we are trying to break in a barrel by smoothing
the surface without cutting, and it seems to me that process would go
much quicker if we used something on the inside of the bore that was
closer to the hardness of the barrel instead of lead or copper. So I
started trying the steel wool and oiled patch technique on new barrels
before shooting them. I use it about as tight as I can get in the bore and
wear out a steel wool pad or two in about 15 minutes, then I go and
shoot the rifle.
How well does it work you might ask? On a few occasions, I have built a
new rifle and taken it to a match without ever having fired the rifle. All
have performed flawlessly in their first match and several times I won
the match or set a record with them. On one occasion, I set a new 300
yard range record with the first 13 shots out of a barrel. This method
has become a service we offer to our customers here in the shop and I
have shared the technique many times with others.