This article is provided by RSI as an instructional aid.

If you have never used a cleaning solution that smells like ammonia
and never seem to be able to duplicate a tight group, this article is
for you.   You may be doing everything possible to achieve a perfect
rifle load but if your barrel fouls too quickly your effort is wasted.

Let's start with the basics. 1) For the purpose of this article we are
addressing only the most common form of fouling caused by copper left
in the bore from bullets fired with smokeless powder.

2) It takes several shots to first heat then "foul" a cold clean
barrel so velocities stabilize and optimum accuracy can be achieved. 
This is because initial shots through a clean barrel produces
different frictional energy until lube is blown out and the bore is
coated with powder residue and/or copper so bullet friction begins to
stabilize.

But the copper keeps building up!  Soft metals gall and stick to
similar metal.   Each round fired through a barrel will deposit a
little more copper until eventually accuracy deteriorates.  Once a
barrel is fouled successive shots will not remove the copper.

3) Copper fouling is usually deposited in patches and lumps. 
Resulting in a rough bore which promotes the tearing of the tail
portion of the bullet jacket as it passes through the bore. This adds
air turbulence at the base of the bullet so it does not fly as true.

4) All barrels foul.  It is simply a matter of how many shots are
needed to first stabilize velocity then how quickly it fouls so
severly the gun starts "tossing flyers".   Oviously if it takes nearly
10 shots for velocities to stabilize and at that point the barrel is
fouled so severely accuracy is impossible, you have a problem.  The
barrel is called a "fouler".

5) Copper is easily removed with Sweets, Butch's or Barnes Copper
solvent. If it does not stink like ammonia it is probably no good for
removing copper despite manufacturer's claims.  Ammonia has been the
chemical of choice for removing copper from barrels for over 100
years.  To my knowledge there is no detrimental affect providing the
ammonia solution is removed before a gun is stored.  The Outer's Foul
Out electronic cleaners also work well for extremely fouled barrels
but any ammonia based copper solvent will remove NORMAL copper build
up.

6) New commercial barrels may foul horribly after only 10 shots.  Even
custom barrels may foul after only 20 or 30 shots.  Both can be
improved. Here's how.

SHOOTING IN A BARREL

First the barrel should be new or cleaned thoroughly of all copper
down to bare steel.  Using an Outer's Foul Out is the easiest way to
remove copper from a barrel that has never been properly cleaned.

Once the bore is cleaned down to bare steel shoot a round and use an
ammonia based copper solvent as directed by it's manufacturer.  Most
instruct you to first run a patch wet with a powder solvent such as
Hoppe's no. 9 through the bore to remove powder residue, then a dry
patch so you are down to copper.  Then run a patch wet with the copper
solvent thru the bore and wait a few minutes repeating this last step
until no blue/green copper residue comes out on the patch.  Once the
copper is removed run a dry patch through to clear the ammonia. Some
shooters wet a patch with water, then swab the bore again with a clean
patch to remove all trace of ammonia.

Repeat this process until after a single shot you see no copper
residue on the first patch wet with copper solvent then go to two
shots at a time, then three, etc.  Ideally you will want to be able to
shoot at least 10 shots before you get copper deposits in the bore. 
This should allow 15 to 20 shots before there is sufficient copper
fouling to "Toss Flyers" and velocities should stabilize quicker when
starting with a cold clean barrel.  This is a time consuming process
and may take an entire day, but the effort is well worth it.  
Eventually the gun will clean with just a few patches and no scrubbing
will be required. Once the barrel is properly "Shot In" NEVER  use a
stainless brush.  I don't even use a bronze brush!    Always coat a
clean dry bore with oil before it is stored.

Why This Works No matter how a barrel is manufactured there will be
microscopic voids in the crystalline structure of the steel.  Copper
will be deposit in these voids.  Because like metals tend to "stick"
to like metals, more and more copper will accumulate until the fouling
material is higher then the surface of the bore.   This is when
accuracy will seriously deteriorate and you feel roughness when a
patch is pushed through the bore.  Copper solvent removes copper from
the voids so each successive shot through a properly cleaned
bare-steel barrel "sloughs" surface steel molecules into/over the
voids until they are nearly closed.

No voids, smoother bore and less fouling.  It's that simple.  Running
a stainless brush through the bore will certainly add microscopic
scratches open open the voids again.  This is why if you do choose to
use a brush on a good bore always push thru the bore from the breach
and never pump the brush back and forth.

Yer Ol' Huntin' Guns If you have never had a barrel cleaner that
smells like ammonia I bet you are wondering about that old hunting
rifle that no longer seem to shoot like it once did.  If the rifle
never had "the stinky stuff" in the bore, it is probably copper
fouled.  Just clean the copper out and it should shoot factory ammo
like it used to.  And, if you work up a good load... it may shoot half
inch groups!

Visual Inspection Copper fouling normally starts at the barrel's
throat and progresses to the muzzle.  If you can see red copper
between the lands at the muzzle you are definitely copper fouled.

Jim Ristow, Recreational Software, Inc. info@shootingsoftware.com
http://www.shootingsoftware.com