Which things to avoid that will damage the barrel

Personally I have never damaged a barrel.
And certainly not with a bronze or nylon bore brush.

I would not suggest using a stainless steel brush in any good barrel.
But I do use them in older restoration work on very old neglected guns.
Sometimes you gotta do what you gotta do.

I do own, or have owned several old Winchester lever-actions with completely worn out funnel shaped muzzles caused by 100 years of cleaning rod wear.

But those barrels were relative soft steel, and who knows what kind of cleaning rods they had used on them through all those years.

The other leading cause of barrel damage I have seen is from shooting corrosive primed GI surplus ammo and not cleaning at all, or properly afterward.

That's about it.

rc

Clean your bore with a good one piece coated rod from the chamber. Use cleaning equipment that's 'softer' than your barrel. Be careful to not wear the muzzle / crown with jags / brushes. If you’re cleaning a rifle that requires cleaning from the muzzle, use a bore guide (a bore guide is a good idea for bolt guns too, keeps solvents out of the action). Carefully read and follow instructions on solvents; some are aggressive and can damage your bore. Remove all solvents and oil the bore and chamber after cleaning (a fouled bore stores OK, a clean / non-oiled bore does not).

As RC said, corrosive ammo can damage a bore if not properly cleaned. Some old surplus ammo has noncorrosive powder, but the primers are corrosive.

I generally don't see too many things done to barrels that causes horrible damage. I occasionally see rifles that are cleaned improperly and the crown is trashed. Military guns that have been cleaned from the muzzle with steel rods often are destroyed for the first 1 - 2 inches. In cases where it is appropriate I will part off the muzzle and recrown and lap. On milsurp guns this can really make an improvement. Getting rid of the shoddy loose last inch or two and getting a good clean crown can wake them up.

The vast majority of damage I see is due to storage neglect. Hunting guns that have been out in the rain then stored. Large volumes of rust from storage with moisture in the bore that causes rust pitting. I RARELY use a stainless brush...but on a really rusty bore I will make a couple passes to knock off the crust. I do occasionally use Scotchbrite as a patch to recover a rusty bore. Flitz on a cotton patch can produce a good shine in an otherwise questionable bore.

Recovering a barrel that has had LOTS of corrosive rounds...is pretty much beyond saving. Some are so dark and rough...it is like looking through a sewer pipe.

I did shove a so called bronze brush through the bore of my Ranch Rifle many years ago. It turns out it was actually made of bronze plated hard steel wire. I became suspicious at the amount of friction it had going through the bore and the heavy deposit of gray paste that dropped out upon pulling it out of the bore. I dumped some of the material on a glass slide and gave it an inspection under the microscope and found hundreds of thousands of little curly que shavings of my barrel piled on the slide. The rifle still shot fine but I should have made Outers buy me a new barrel.

Shimitup,
With no more information than you provided, I would bet that the brush dislodged leading from your barrel. Cutting shavings from steel is no easy task, and I would be shocked if any discernable amount could be cut in a few passes of a steel brush. I have spent more hours than you might expect cleaning (the exterior) of basket case guns with steel brushes, and would love to find one capable of removing a discernable amount of metal even if significant effort is required.

Edit: Did you check to confirm that the shavings were attracted to a magnet?

Indeed I did verify that, I also verified the bristles were steel by cutting some loose and letting them stick to a magnet. BTW I only shoot jacketed in that gun.

RC,

Philosophical time......

How do you know that you have not harmed a barrel? I have wondered this several times because as I clean I wonder if I am doing damage. I know I am using my Dewey rods, bore guides, proper sized quality tools, brushes and no stainless but still I wonder how do I know?

I have been debating buying one of those borescopes that is always advertised in Handloader just to figure out what is down that barrel that I work so carefully on. While expensive the price does not seem to be going down much lately.

So my question back to you would be "How do you know you have not damaged a barrel?"

I avoid stainless brushes. Ever see somebody sawing away at a barrel with a cleaning rod? You know, getting their back into it? I avoid that. Gentle does it.

I could afford to buy a borescope, it would be fun to have one. I just haven't talked myself into one because if the gun shoots who cares what the bore looks like?

Actually, I still want to get one. Maybe if I retire next month.

I think the cost of the borescope would just be the initial investment; the real cost would be from re-barreling all your rifles. Some things are just better not seen.

I use VFG pellets from Brownells. Their "aggressive" pellets will get out the crud/fouling (especially when used with J-B Non-embedding Bore Cleaning Compound/Kroil ) with no damage!! If you follow this up with fine pellets and J-B Bore Bright/Kroil you can clean up a horrible looking bore to at least "shootable" condition. In addition the Kroil leaves an excellent anti-corrosive film behind.

If you start with a good bore, it will shine like glass when you use this method!!

I also use only graphite rods!!

With bore guides!!!

Good Luck!!