UPDATE ON BORE CLEANING

Sometime back a text file containing opinions and suggestions on 
the cleaning of rifle barrels was posted in Library 14 of the 
Outdoors Forum.  Later, excerpts from a discussion thread on this 
topic were also posted.  Over the past months I have conducted 
numerous experiments in bore cleaning and have been in near-
constant contact with others conducting similar and related 
research.  As a result of this, I believe further discussion of 
this topic is in order.

RISK TO RIFLE BORES

It is an axiom among firearms authorities that more barrels have 
been ruined by improper cleaning than have ever been worn out by 
shooting.  This may be more true today than at any time in the 
past.

Over the past few months there has been a rapid increase in 
reports of rifle barrels which have been irreparably damaged by 
common cleaning solvents and practices.  In at least two 
instances, brand-new stainless-steel match barrels have been 
ruined in less than fifty shots, and there are many others where 
accurate service life has been significantly reduced.  There are 
two types of products associated with this damage.

1. High-ammonia copper removers

Bore-cleaning solvents containing high concentrations of ammonia 
are implicated in the majority of the damaged barrels we have 
examined.  Damage takes the form of many very small pits, 
"frosting" of the bore surface, and cracking of the bore in the 
throat, leade and rifled area immediately forward of the chamber.  
Chemical pitting and etching of the surface apparently cause a 
weakening of the steel's crystalline structure which leads to 
cracking under the heat and pressure of firing.  This is believed 
to be the result of an electrolytic reaction which takes place in 
ammonia between the various ingredients of barrel steel and 
particles of copper imbedded in minute surface flaws in the bore.  
Careful examination with a high-magnification bore scope indicates 
that pits in the bore surface become larger and more numerous with 
each firing and subsequent cleaning with copper removers, which 
seems to confirm the electrolytic theory.

Sweet's 7.62 Solvent is the most commonly reported solvent in 
these cases, probably because it is used by more shooters than 
other copper removers.  Other implicated products are Shooter's 
Choice Copper Remover, Barnes CR-10 and Hoppe's Benchrest 9.

2. Electrochemical bore cleaners

Barrels cleaned electrically via "reverse plating" of copper onto 
an electrode in the presence of an electrolyte show the same 
symptoms as those cleaned with ammonia solvents, although these 
symptoms occur at a less rapid rate.  This comes about because 
copper is a less "noble" metal than anything in barrel steel and 
is actually less strongly attracted to the electrode than the 
metals in the steel alloy.

Involved products include the Outers Foul Out and Foul Out II, 
similar devices marketed by individuals, and devices made from 
plans which have appeared in publications for shooters.  Some of 
the latter are particularly pernicious, since users are instructed 
to use household ammonia as an electrolyte, creating a double 
whammy.

WHAT IS SAFE?

There is some division of opinion as to what constitutes a safe 
product for bore cleaning.  Expert #1 recommends that only bronze 
brushes and Shooter's Choice be used, saying that he has seen no 
signs of abnormal wear or cracking in several dozen barrels 
cleaned exclusively with these products.  Expert #2 recommends 
that only oil and RemClean or other diatomaceous-earth abrasive 
cleaner be used.  #1 says RemClean  wears barrel steel; #2 says it 
does not, but bronze brushes will.  I personally believe there is 
probably some justification for both points of view, and use 
either RemClean or Shooter's Choice according to which seems to 
work best in a particular barrel at a particular time.

What seems certain at this time is that there is NO currently 
available product which will quickly and without labor remove 
large amounts of copper from a barrel which does not have at least 
the potential for harming the barrel.  Whether these products 
ALWAYS damage barrels or only do so under certain circumstances is 
unknown  It is possible their use might be justified in barrels 
that have accumulated so much fouling that the fouling itself is 
likely to cause greater damage than even a harsh cleaning product.

HURRY-UP BREAK-IN ROUTINES

Some shooters have advocated "clean & shoot" regimens to rapidly 
condition rifle bores. Two main variations are known to me.  In 
the first, the bore is thoroughly cleaned and dried after firing 
from one to three shots, and this is repeated until little or no 
copper fouling occurs.  In the second, a series of shots are 
fired, each followed by running two or three solvent-soaked 
patches through the bore and allowing time for the solvent to 
work; the bore is not completely cleaned after each shot, nor is 
the solvent wiped out of the bore before firing again.

The first method does seem to significantly reduce copper fouling 
after a few shots, and to the best of my knowledge does not harm 
barrels as long as one of the safer solvents (Shooter's Choice or 
standard Hoppe's #9) is used.  The second method was involved in 
both of the two cases I know about where barrels were completely 
ruined in only a few dozen shots, and I personally consider it 
EXTREMELY hazardous to barrels.  Under no circumstances should 
Sweet's 7.62 or other high-ammonia solvents be used in conjunction 
with a fast-break-in routine.

I have seen no evidence whatsoever that a clean & shoot break-in 
does anything that would not occur naturally over the course of 
150 to 200 shots in a barrel which is properly cleaned after every 
ten to twenty rounds.

THE MYTH OF THE CLEAN BARREL

Over the past couple of decades shooters have been pretty 
constantly bombarded with the advice that barrels must always be 
kept as clean as possible if they are to shoot their best.  I 
think this advice contains a germ of truth, in that the very best 
and most accurate barrels often produce their tightest groups 
right after cleaning, but I believe that applying it as a 
generality leads mostly to frustration.  There are many, many 
barrels which do not shoot their best until after a certain 
minimum number of shots have been fired and which suffer a loss of 
accuracy following a thorough cleaning.  The mechanism here seems 
to be that carbon left by powder combustion provides a surface 
which is beneficial to accuracy in many if not most barrels.  The 
owner of such a barrel is ill-advised to scrub it out after every 
few shots.  It is far better to do enough firing and experimenting 
to determine what an individual barrel's needs are, then use that 
barrel in the way that works best.

The potential for damaging a barrel by cleaning it, whether by use 
of harsh chemicals or by inappropriate techniques, will be kept at 
a minimum by cleaning the barrel no more than is required to keep 
it shooting well.  The idea that perfect cleanliness will result 
in perfect accuracy is a chimera.

--Dan Hackett