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Old 11-10-2010, 03:49 AM   #1
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Default Shooting down gun myths, Muzzle wear from cleaning

Here we are again. This is one I did at another site but now I have more information.. I have been doing some research on this subject because I still see gun writers quoting old wives tales.
The subject is cleaning guns from the muzzle.
And how this can wear out the barrel. In my first myth buster I stated that it could not happen because it would take millions of strokes with a aluminum rod to even show anything but marks of aluminum on the steel. Aluminum is softer than steel. But others said that it wasn't the aluminum that wore out the steel but the carbon residue. Sounds good but how many times do you have to stroke the bore to get out the carbon? Three times? five times? Seven times? And how much carbon is left in the bore after the first stroke? Not much. You are gotting more residue from the bullet that is copper residue after the first two or three times you go in and out.
But there are still those that claim that they bought a rifle that was all worn out at the muzzle end of the barrel which they attributed to cleaning the gun from the muzzle. I too have seen rifles worn out at the muzzle but I didn't immediatly jump to the conclusion that it was the cleaning from the muzzle that did the dirty deed.
Right now in my shop are several military rifles. These are bolt actions that have seen a lot of action. The headspace is sloppy and the outside of the gun shows wear, tear and stains from actual combat useage. And they have wear in the muzzle of the barrel. Two of them do. The other one was arsenal refinished and the first inch of the inside of the barrel is counter bored out. Why? to get rid of the worn rifling.
Now these rifles were actual combat rifles that were used in the war (WWII) and from my own experience in the Army they probably did not get one cleaning a week. If they were lucky. But they had somewhere near several thousands of rounds of ammo go through their barrels. (maybe more if they were used in Korea too)
I called my buddy from the Army who is an armorer. I asked him why the Army had the barrels counter bored in some of the rifles when they were sent back to the Armory. He stated that was to get rid of the worn riflings in the barrel at the muzzle. Well that was what I figured but it flies in the face of the rest of the facts. First these rifles were not cleaned often. Second they were shot more than any civilian rifle.

The more I thought on the puzzle the more I went back to my College Metalurgical 101. The way steel can be eroded, (worn out) is by heat, pressure, abrasives and oxidation. Now these guns did not get a thousand strokes of cleaning in their lifetime (judging from the bores I am seeing now) but they all had worn riflings at the muzzle end. Lets look at the other ways that steel can be eroded. Heat and pressure just jumps off the paper.

Here is the situation as I see it. As the bullet goes up the barrel behind it is approximately 60,000 psi of pressure and maybe 1200 deg of heat or more. Now this is normal and the steel in the barrels are such that it will resist this for years and thousands of rounds. The heat is caused by the burning powder of course, and the powder can burn in the little barrel because it has it's own oxygen inside it's kernals. But let's get out to the end of the barrel when the bullet exits. What do you see?
A big blast of fire. At night it is a tremendous fireball. Where does this fireball come from? Well the powder is just about out of it's own oxygen and when the bullet exits there is suddenly a new supply of oxygen. Lots of oxygen! And the powder that has not burned completely goes boom! (that is what you hear when you shoot a gun, the powder gas going sonic) And when that "enriched with new oxygen" powder goes boom it also raises the temperature of the burning gas. And that burning gas is where? In the last inch of the barrel. Steel can be eroded by heat, pressue, abrasives, and oxidation. There you have it. The heat of that super hot gasses is responsible for most of the wear on the inside end of the barrel. Not the cleaning rod.
Sarge the scientist

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Old 11-10-2010, 02:48 PM   #2
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A few thoughts/questions:
1. Did they use aluminum cleaning rods in WWII or Korea?
2. When I measure barrel temperate the chamber is significantly hotter than the muzzle
3. How many 'thousands' are needed to wear out the muzzle? I have over 8,000 rds through a Remington LTR .308 it still shoots submoa groups. As I understand it the first thing that will wear out and start degrading accuracy is the chamber area. That can be recut and the gun will shoot fine.

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Old 11-10-2010, 03:31 PM   #3
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Sarge I have thought this way for a long long time.

How can cotton and aluminum wear out a hardened steel or SS barrel.

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Old 11-10-2010, 03:39 PM   #4
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What about those who say you have to use nylon bore brushes instead of brass?

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Old 11-10-2010, 05:45 PM   #5
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Quote:
Originally Posted by lonyaeger View Post
What about those who say you have to use nylon bore brushes instead of brass?
Lon,They're the same people that say an aluminum/steel rod will damage your bore.
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Old 11-10-2010, 05:50 PM   #6
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I had read in the past that nylon bore brushes are actually harder on your barrel that the brass ones. I just use brass brushes and make sure that once the brush is in the bore that I never stop and never change directions once I start the pass of the brush through the bore.

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Old 11-10-2010, 06:07 PM   #7
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im not sure your all the way ther on it but i think your very much on the right track. it prolly has something to do with that last bit of burning time and how much or little powder is left what weight charge what type powder and corosivity of the primers.

ive always cleaned from the breach end so as not to wack the crown. military rods are made of mild steel from ww2 aluminum was very pricey and almost solely reserved for aircraft if im not mistaken.

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Old 11-11-2010, 03:20 AM   #8
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If you look at a barrel of recent manufacture which has thousands of rounds through it, you will see the rifling is eroded at the throat while the muzzle looks relatively pristine. Early military barrels are a slightly different story because the ammuniton was corrosive and the barrel steel was different in composition.
Aluminum rods damage bores in two ways. First, because they are soft, grit become embedded in the rod and cuts the barrel. Second, aluminum oxide forms on the surface of the rod and abrades the barrel steel.
Having said this, I think it would take some time to wear the barrel appreciably by cleaning from either end. GD

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Old 11-11-2010, 04:04 AM   #9
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Quote:
Originally Posted by ccd8541 View Post
A few thoughts/questions:
1. Did they use aluminum cleaning rods in WWII or Korea?
2. When I measure barrel temperate the chamber is significantly hotter than the muzzle
3. How many 'thousands' are needed to wear out the muzzle? I have over 8,000 rds through a Remington LTR .308 it still shoots submoa groups. As I understand it the first thing that will wear out and start degrading accuracy is the chamber area. That can be recut and the gun will shoot fine.
Nope you are right they did not use aluminum cleaning rods in the military. They used steel cleaning rods. But very infrequently. The rifles I used in basic training had been cleaned more than any rifle in the world. But they did not show wear at the muzzle and they shot darn well.
Yes the temperature in the chamber area is hotter than the end of the barrel. But it is not the chamber that is hot or worn. It is the forcing cone. The chamber is protected by the brass cartridge. The forcing cone is not parallel with the barrel. It is cut at an angle(cone) and there fore gets more of the original and hottest blast of burning powder gas. The powder gas hits the forcing cone and the angle of it causes additional pressure to the steel that the rest of the barrel doesn't get. Except at the end of the barrel when the extra oxygen explodes the powder.
Final; I wouldn't know why your rifle is not worn out but just count yourself lucky that you got a precision made with tight tolerances rifle. I wish they all were made like yours.
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Old 11-11-2010, 04:37 AM   #10
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Originally Posted by lonyaeger View Post
What about those who say you have to use nylon bore brushes instead of brass?
Very likely they sell nylon bore brushes. I have felt for a long time that a lot of the gun myths are perpetuated by gun accessory companies that sell some accessory that will solve a problem. And the gun writers repeat old myths because some well known and famous gun writer or gunsmith said it many years ago. And to challenge an icon of virtue would be sacrilegious. But they don't realize that what was the norm waaaay back in those times doesn't necessarily stay true for our modern CDM produced and modern steel guns of today.
A long time ago, well not that long ago, I saw a demonstration at a gun show in Wichita Ks. A fellow had a new Ruger Blackhawk set up on a table. He had made a little motor with a bell crank on it and attached it to a aluminum cleaning rod with a bronze brush. Above the set up he had a can with a little hole in it. The can was filled with gun cleaning solvent and would drip out of the hole about once a minute or so. The solvent would fall on the cleaning brush as the threaded end came out a small distance. The motor ran pretty fast and pushed the cleaning rod in and out all day. At the end of the day, the motor was stopped and the gun was examined for wear. He had measured the inside of the bore in three places including the crown. There was no appreciable wear in the riflings or the bore. In fact the aluminum rod was worn down and there was some aluminum deposited in the riflings at the crown.
That is the first time I found a busted myth in public. And I learned a lot from it.
Sarge
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