From: Gale McMillan <" gale"@mcmfamily.com>
Newsgroups: rec.guns
Subject: Re: .22LR barrel burnout from HV ammo?
Date: 11 Jan 1997 13:57:50 -0500

Walter Taylor wrote:
# 
# llarkin@fox.nstn.ca (llarkin) wrote:
# #In article <19970108230300.SAA17571@ladder01.news.aol.com>,
# #gsanf387@aol.com says...
# ##
# ##Question: Is there any truth to the statement "Using high velocity ammo
# ##will ruin a target barrel in 3000rds?" I have a semiauto(10/22T) that
# ##functions best with the higher velocity cartridges(although is more
# ##accurate with std. velocity)
# ##
# #
# #It would take WAY more than 3000 rounds to wear out a .22LR barrel. In
# #fact, I'm not even sure it's possible. In any case, the use of std./hi
# #velocity ammo is irrelevant. I have heard rumors of some european
# #ammunition manufacturers using lead free priming in their target ammo,
# #which is mildly abrasive.
#
#
# The only .22 LR I have seen shot out was a micro-groove with more like
# 3000 bricks through it.


Small bore ammo still has lead in it.  They put glass in it to increase
the sensitivity that  usually ends up in the lower half of the barrel
and the next round goes over the top of it.  It makes the barrel look
frosty but it doesn't seem to hurt anything and never seems to get any
worse as you shoot.  It doesn't hurt the accuracy any.  I have looked
through Wigger, Bashams.and most of the International teams rifles over
the last 30 years and they all looked the same.  Don't worry about it.

Gale McMillan

From: Gale McMillan <" gale"@mcmfamily.com>
Newsgroups: rec.guns
Subject: Re: Help on barrel burnout
Date: 12 Mar 1997 18:21:00 -0500

r_tech@earthlink.net wrote:
 
# How do you determine when a barrel is burned out?  Does its accuracy
# go to hell or what?
# 
# My rifle is nowhere near that if that is the case, but I have seen
# lots of posts here regarding barrels being burnt and or worn out.

A barrel is gradually burned out by erosion of the throat and bore. 
First the rifling in the throat starts to round off rather than have
sharp corners.  Then it starts to disappear gradually until you no
longer can touch the rifling with the bullet.  About this time the
entire bore starts to heat check.  That is when tiny shallow cracks
start appear all over the throat area and a few inches down the barrel
that look like the mud flats in a dry lake bed.  Continual firing will
cause these small squares to pop out causing the bore to get rough and
hard to clean.  Performance starts to deteriorate about the time you
can't touch the rifling with the bullet and deteriorates gradually. 
When a barrel is new if you shot it a hundred groups you would get say 4
or 5 groups that were very small, 8 or 10 that were small 60 that were
average and so on.  As a barrel goes, the number of smaller groups get
fewer and fewer.  The big groups don't get bigger but your aggregate
gets larger.  When it is time to replace it is when you feal you can't
live with the agg. that it is shooting.  I have seen magnum match rifles
that were still shooting respectable scores and didn't have any rifling
visible for several inches down the barrel.  It wouldn't beat a good
rifle but still shot pretty good.  I always changed my barrels before
they showed any loss of accuracy because I couldn't afford to spot my
competitors any.  As for a hunting barrel, don't worry about it because
you won't shoot it enough to see any change in your off hand shooting.

Gale McMillan

From: Gale McMillan <" gale"@mcmfamily.com>
Newsgroups: rec.guns
Subject: Re: Barrell life -  EROSION v. CORROSION
Date: 28 May 1997 08:57:50 -0400

-Faber,S.R. wrote:
#
# In article <5ltclk$cgk@xring.cs.umd.edu>, John Wilder <jwilder@llnl.gov> wrote:
# #There are erroneous assumptions here.  Bullets running down the barrel do
# #not wear it.  Erosion always is at the throat, the region of least bullet
# #velocity.  Erosion is due to high temperature of the barrel surface with
# #the resultant effect on the metal.  The higher the performance of the
# #rifle, the greater is the heat conducted to the metal surface.  Since the
# #region right in front of the case mouth is subjected to the longest time
# #period and the highest pressure, it erodes the most.
#
# Recently in Precision Shooting authors have suggested that the limiting
# factor isn't the erosion, but the stress induced corrosion/cracking which
# occurs at the peak pressure point just forward of the throat area you mention
# that is subjected to the highest surface temperature.  Their finding is that
# the bore becomes constricted at the peak pressure point due to the corrosion
# and cracking and this is the cause of the reduced accuracy more than the
# throat effect.  Comments?
#
# Steve
#
# http://www.mcs.net/~sfaber              Internal Ballistics Page
#                                new additions:  analysis of a pressure curve,
#                                                         Barsness' rule

 A couple of points are in error.  Peak pressure and temperature is as
much as 8 inches down the barrel.  The loss of accuracy is do to the
throat moving forward and allowing the bullet to jump into the rifling.
As long as you can advance the bullet seating depth to put the bullet
back in the same relation to the rifling you will not experience a loss
of accuracy.  The Marine match rifles by the time they retire a barrel
the rifling has disappeared for 6 to 8 inches.  That's 1200 rounds.  The
first 800 rounds are for the masters and then the kids get them.  It is
true that erosion is caused by the blow torch effect of powder gasses
and solids striking the rifling.  One forgets that a large amount of
powder travels down the barrel at the speed of gas.  If you really want
to see the damage this can cause look at the cone of a muzzle brake on a
50 cal and see where powder kernels have peaned the hole over until it
causes the bullet to strike the brake.  In barrels that have been
subject to erosion for many more rounds than you would think was their
normal life you will see erosion and heat checking within a couple of
inches of the muzzle.  The throat is the point in the barrel that sees
the heat first and for a longer period of time each shot so it is little
wonder that the throat is the first to show erosion.  As for the
corrosion, I believe someone is confused about the meaning of the word.
A quick trip to the dictionary defines it pretty well.  The heat
checking that they refer to as corrosion is in fact a part of the heat
erosion and it also starts first at throat and works it's way forward.
Having had the opportunity to inspect match barrels regularly from their
first shot and routinely after every match till the end of their life
for more barrels than I like to think about you get a good idea of the
progressive wear and life of a barrel.  You must have this information
to make an intelligent decision on when to change it so that you don't
carry it so long that it effects your ability to win and don't change
them so often that you are wasting money.  As for the authors assumption
that it is corrosion I won't ask them how many barrels they have made If
they don't ask me how many articles I have written.

Gale McMillan

From: sfaber@ihgp1.ih.lucent.com (-Faber,S.R.)
Newsgroups: rec.guns
Subject: Re: Barrell life -  EROSION v. CORROSION
Date: 29 May 1997 21:13:44 -0400

In article <5mha4e$l1h@xring.cs.umd.edu>,
Gale McMillan  <" gale"@mcmfamily.com> wrote:

# A couple of points are in error.Peak pressure and temperature is as
#much as 8 inches down the barrel.  The loss of accuracy is do to the
#throat moving forward and allowing the bullet to jump into the rifling.
..
# The throat is the point in the barrel that sees
#the heat first and for a longer period of time each shot so it is little
#wonder that the throat is the first to show erosion.  As for the
#corrosion, I believe someone is confused about the meaning of the word.

It certainly appears that throat erosion is the major effect.
It does seem that "corrosion" is a misnomer for the heat checking
and bore constriction unless it could be shown that the iron forms
some kind of compound due to the action of the hot gases.
BB has illustrated how bore diameter variations are critical to accuracy
so I still wonder if there is an important effect there.
It is possible to calculate the pressure vs bullet distance from a
measured pressure curve as in my web page, and the results are consistent
with Internal Ballistic models I have played with.  The greatest bullet
travel distance at peak pressure I've seen is 3 inches - for a .338 Lapua
with slow powder.  I'm not sure exactly how far out the alledged constriction
was from the article.
The gas temperature starts out high - at the burning
temperature- and then decreases with bullet travel and time as energy
is transferred to the bullet and barrel heating, so the gas temperature
will not be quite maximum at the peak pressure point.
The barrel steel surface temperature is proportional to the gas pressure,
temperature, velocity, and time.  Calculations indicate that the highest
steel temperature point is in the throat area due to the above factors which
probably contributes to the high erosion in the throat as you mentioned.
The results also agree with findings in some I.B. references.

Steve

http://www.mcs.net/~sfaber	Internal Ballistics Page

From: Gale McMillan <" gale"@mcmfamily.com>
Newsgroups: rec.guns
Subject: Re: Barrell life -  EROSION v. CORROSION
Date: 30 May 1997 11:26:51 -0400

-Faber,S.R. wrote:
#
# In article <5mha4e$l1h@xring.cs.umd.edu>,
# Gale McMillan  <" gale"@mcmfamily.com> wrote:
#
# # A couple of points are in error.Peak pressure and temperature is as
# #much as 8 inches down the barrel.  The loss of accuracy is do to the
# #throat moving forward and allowing the bullet to jump into the rifling.
# ..
# # The throat is the point in the barrel that sees
# #the heat first and for a longer period of time each shot so it is little
# #wonder that the throat is the first to show erosion.  As for the
# #corrosion, I believe someone is confused about the meaning of the word.
#
# It certainly appears that throat erosion is the major effect.
# It does seem that "corrosion" is a misnomer for the heat checking
# and bore constriction unless it could be shown that the iron forms
# some kind of compound due to the action of the hot gases.
# BB has illustrated how bore diameter variations are critical to accuracy
# so I still wonder if there is an important effect there.
# It is possible to calculate the pressure vs bullet distance from a
# measured pressure curve as in my web page, and the results are consistent
# with Internal Ballistic models I have played with.  The greatest bullet
# travel distance at peak pressure I've seen is 3 inches - for a .338 Lapua
# with slow powder.  I'm not sure exactly how far out the alledged constriction
# was from the article.
# The gas temperature starts out high - at the burning
# temperature- and then decreases with bullet travel and time as energy
# is transferred to the bullet and barrel heating, so the gas temperature
# will not be quite maximum at the peak pressure point.
# The barrel steel surface temperature is proportional to the gas pressure,
# temperature, velocity, and time.  Calculations indicate that the highest
# steel temperature point is in the throat area due to the above factors which
# probably contributes to the high erosion in the throat as you mentioned.
# The results also agree with findings in some I.B. references.
#
# Steve
#
# http://www.mcs.net/~sfaber      Internal Ballistics Page

It has been my limited observation that as a barrel erodes and heat
checks down the barrel the grove diameter gets larger in the area of the
heatchecking until the point that the squares start to pop out when they
may rise enough to restrict the bore but since they are immediately
wiped away this could be a point to be debated.  It can be observed in
badly heat checked barrels that they tend to metal foul worse in the
areas where the checking is the worst.  Generally badly worn machine-gun
barrels display this more than rifle barrels possibly due to the more
frequent cleaning that rifles get.  There could be grounds to argue that
due to the metal fouling in the rough areas of the barrel that the bore
would be restricted due to this fouling but I question if the build up
of copper would equal or surpass the amount of metal washed away on
properly cleaned barrels.  It all seems a when a barrel reaches this
point it is many rounds beyond it's useful life so this seems much like
the argument of the chicken or the egg.  One observation that I have
made is you can take a barrel that at 600 rounds shows a given amount of
heat checking and cut it back until there is no trace of checking and
rechamber it and in about 1/3rd. to 1/2 the amount of rounds through it
the heat checking will be just as bad as it was before you cut it back.
This tells me that it has an accumulative effect.  We used to try to get
more life out of a match barrel but unless a shooter does his own work
at today's labor cost it doesn't pay to set one back.

Gale McMillan