BRUSH DAMAGE

[Webster]

After reading post about the pro’s and con’s of using a bronze bore brush I decided to run an experiment to see if the bore is damaged by a brush. I took a 6” stub cut off the end of a Douglas SS 6mm. barrel purchased in 1978. I cut 1” sections from the stub and cleaned the pieces ultrasonically. I then lubed a used bronze bore brush with gun oil. Next I put it in an electric drill and ran it for one minute at low RPM in the bore. Then I cross-sectioned the pieces, ultrasonically cleaned them and took pictures of the bore using a scanning electron microscope. The rifling marks run length of the barrel. Any scratches 90 degrees across the lands and grooves have to be from the brush. The amount of damage was scary.

 

[BoydAllen]

Well, that does it. I'll have to stop chucking my cleaning rod in a drill! If you shoot, barrels get dirty, chemical cleaners have their limits. The question is whether very very very small scratches, that run parallel to the rifling hurt anything. I doubt that they do. One thing that you should keep in mind. A mirror finish barrel is undesirable. I will cause jacket fouling problems, which is why something on the order of 320 grit is as fine as custom barrel makers use.
I have a 6PPC fire forming barrel that is alligatored at the throat. The rest of it looks pretty good. The reason that I stopped using it in matches was not because it had lost accuracy. It won its last match, in registered competition, against a respectable field. Throughout its entire life, I cleaned it with a bronze brush. Worry about what matters.

 

[SS427]

How do you know those scratches were not there before? Did you look at a control piece before you ran the brush and scanned it with the electron microscope?

The best shooter use bronze brushes, so it is hard to argue with success. I think you are reading too much into these microscopic scratches. I could be wrong but I'm not giving up my bronze brushes yet.

 

[fdshuster]

I have a Shilen stainless heavy varmint contour, select grade bought new & chambered in 1998 to 6ppc. Last Spring at 2410 documented rds fired started to get occassional flyers & a little more copper. My Hawkeye borescope showed firecracking in the throat. My gunsmith set the barrel back from 24" to 20" & re-chambered. it continues to shoot little, tiny bughole groups, the bore has been inspected from the throat to the muzzle & looks like it has never been fired, and have used nothing but tight fitting bronze bore brushes for it's entire life. I don't plan on attaching my brushes to an electric drill. I think I'll continue to do what has worked for me

 

[FBecigneul]

Webster: I'll not question your test or your results. But, I'll say this; I shoot and then I clean with bronze bore brushes and I don't see where they cut the life of the barrel or have an adverse effect on accuracy. Still, I thank you for your efforts.

 

[BoydAllen]

Webster,
Taking a pointer from Francis, folks who have the equipment, and will take the time to do the work that you published here, are rare. I should have thanked you for your effort, and said that I will look forward to any future information that you care to share. My position is unchanged about the use of bronze brushes, but I could have been less abrasive in my post, since you couldn't see that I was smiling as I wrote it.
Boyd

 

[ndericks]

Webster, thanks for the picture. Could you take one of a bullet? I'm just wondering how smooth they look in comparison.

This is probably a dumb question, but if a mirror finished barrel causes jacket fouling, would "less smooth" bullets help?

Thanks again, Webster, for taking the time to post.

Nick

 

[Forum Boss]

Webster,

Thanks for the test. You results are very interesting to say the least. It may be easier to illustrate the effect with before and after shots of a crown. And to eliminate the criticism that no one spins a brush in a bore, I would simply run the brush back and forth across the crown.

I've seen the damage myself with a 4X loupe after 8-9 agressive cleaning sessions. Crown edge before = sharp, straight. Crown edge after = looks like sharks teeth.

NOTE: This is NOT suggesting people should stop using bronze brushes. That is not my point. But I do suggest, consistent with recommendations of John Krieger, Tim North and others, that you remove your bronze brush after it goes through the bore, flush it clean, and only then send it back through... in the same direction, breech to muzzle. It is the process of reversing the tines of the brush across the crown that causes ragged wear over time.

 

[BoydAllen]

I have attached a picture taken of the crown of a well used, and brushed barrel, with apologies for the quality. Barrels are not perfect mirror finished pieces. This one shoots well, under .2 MOA under perfect conditions. The question is, how big does a scratch have to be before is shows up on the target? This crown has a very small chamfer. There may be some slight texturing from cleaning. Can I see a difference at the target? No, I can not. In short range Benchrest, taking off a fraction of an inch and recrowning every few hundred rounds is probably a good idea. Barrels that are shot wear out. I have not seem one stop performing because of crown damage due to cleaning. Now... bad rod technique, over use of abrasives, and loose fitting bore guides are another matter. Fix the worst things first. If you wish to keep a pristine barrel, don't shoot very much, and have a lot of time available per cleaning. Short range Benchrest competition is not like that.

(If you look carefully, you can see what ratchet rifling looks like.)

 

[Webster]

I had about six pix. Two of the new bore and four of the brushed bore. I didn't upload them properly, so only one got in the article. The corners of the lands were rounded in some areas. Bushing would be along the lands and not across so there would be less damage. I was surprised by some of the comments. I was just trying to show that even though bronze brushes are much softer than steel they cause scratches.

Update: The brush I used was an old one I found particles of iron containing chrome on the bristles. It would make more sense that the brush used to clean a barrel with over 5000 shots had barrel fragments from throat erosion on it and it was these iron particles scratching the bore rather than the bore brush. Does this mean that there are benefits to cleaning the brush with a spray can of carbureter cleaner or ultrasonically cleaning it. The barrel was 29.5 HRC hardness, bronze wire is about 18 HRC hardness.

 

[BoydAllen]

QED....improper use of cleaning equipment can damage a barrel. This includes bronze brushes. Great pictures! It would be interesting to see a picture of the bore ( in front of any alligatoring) of a barrel that had been shot out, and which had been cleaned with the normal back and forth cycling of a a bronze brush for every cleaning. Also, I think that it is safe to say that some of the reaction was really a carry forward from previous brush or don't brush, and brushes should not be pulled back through the bore discussions. I think that sometimes instructions are given that assume a prevalence of inadequate equipment and poor technique. given what I have seen, there is probably some justification for this approach.

 

[bozo699]

Webster,
Thanks for the pics,
I don't know much about electron microscopes. I cant tell from the pics if there scratches or if it is some kind of buildup, but if there scratches, thats amazing that a bronze brush with oil on it could scratch a steel barrel in that short of time?
it makes one think, I as well am going to continue using bronze brushes but I think I will take more care when entering and exiting. If you can find any more barrel sections I would definitly be interested in seeing before and after pics of normal brushing, effects on dragging back over crown,effect on not using a bore guide and just slamming the brush down the bore as I have seen people do. I think you have a pretty interesting subject here and the equipment to do it. I may be able to get you a few take offs. Good luck with any further experiments on the subject.
Wayne.

 

[dreever]

I do know this. Clean your barrel with just patches untill they come out nice and white. Then make a pass or two with a good quality nylon brush and solvent unscrewing it at the muzzle every pass then patch again. You'll now get more black from a barrel that you thought was clean. Patch this out again untill you get white patches. Now repeat the above with a bronze brush, and again you'll get black on your patches.
So does this mean that nylon brushes clean better than just patching and that bronze brushes clean better than nylon? Don't know. Maybe......you decide.

Danny

 

[whiskey08]

such a short time with the rod chucked in a drill? you can bet that multiplied what happens during normal brush use.

 

[BoydAllen]

You might want to spend some time with a bore scope before you make that leap. There is a reason that he had to run the brush across the rifling with a drill to get something to take pictures of. If he took a picture of the inside of one of my barrels that is brushed almost every time that it is cleaned, with a bronze brush, there would have little to point out. Rifle bores are not texture free when they are new. The issue is whether meaningful changes in surface finish are caused by careful brushing.

 

[whiskey08]

"the reason the bore is scored like that is because he had to run the brush across the rifling with a drill to get something to take picture of". Thats the point isnt it? cleaning your bore with a drill will leave damage to your bore. Ive used bore scopes and thats why i brush. I cant get the barrel clean with out them. As for the issue of "meaningful changes in surface finish", (done with out a drill) those have been disuputed and discussed endlessly.

 

[johara1]

I have just scoped my 6.5x47 barrel after 2200 rds and it looks great and still shoots in the low 2's. It never saw a brush and the crown is still sharp,no rounding. I also use Ivy rods and bore guides.......jim