So I don't think a bronze brush with just solvent on it is necessarily a bad thing or hurts the barrel bad by itself.
I guess the basic problem is how it is used. From one person to the next it varies too much.
One pay attention to the brush and flush it from time to time. If you see black particles in the bristles of the brush that is most likely hard carbon from the powder fouling that is coming out. Those hard carbon particles can and will scratch the bore and if you leave it lay in the brush your just dragging the stuff up and down the bore.
Never ever use a stainless steel brush... that's a guaranteed problem.
Also never ever use any brush in conjunction with any abrasive cleaner....that's guaranteed damage as well.
If I use a brush.... I only push it breech to muzzle and when I exit... I remove the brush and then carefully pull the rod back thru. I don't like dragging the brush back over the muzzles crown. Most damage we see from cleaning is the muzzles crown.
You can argue all you want amongst yourselves that the brush is softer than the steel and won't hurt it etc...all I know is how it's used and in conjunction with how it's used.... seems to be a source of damage.
I remember way back in my early days of shooting I bought my first cleaning rod. It was a one piece rod and came with a muzzle guide. I thought that was cool! Looked like this...
View attachment 1547561
anyways I learned the hard way and even though it was brass... by repeatedly running that cone into the muzzles crown and over time it dinged/damaged the crown. Brass is softer than the steel but it damaged the crown to the point that the gun ended up shooting like garbage and I had to pay a gunsmith at the time to recrown my barrel.
So I'm a freak about dragging stuff over the muzzles crown. It's the last thing a bullet sees/touches when it leaves the barrel and any damage to the crown can and will have a negative impact on accuracy.
Then I look at places who use brushes on a regular basis. A couple of ammo/bullet makers that are customers.
I've got ammunition test barrels back and use them for training tools. One barrel (caliber doesn't matter) they where testing bullets/particular ammo that is know for not holding good accuracy and they need to clean the barrel very often. They used a brush in that barrel a lot. The ammo is so temperamental to the barrel being cleaned that they cleaned that barrel on average... after every 37 rounds fired on average. They asked me to look at it after they pulled it from service (over 14k rounds fired) and check the bore and crown etc... for any damage from cleaning and there was nothing that I could really pick it apart from. They documented 404 rounds of cleaning!
They have another barrel in service in 30cal and it's our barrel.... was just told it has over 26k rounds and basically still shooting .5moa or better and currently they are cleaning after every 30 rounds fired and yes they are using a brush not sure if they use it every single time or not. It will be cool to see that barrel after they pull it from service. This barrel is currently getting a
150 rounds fired thru it every single day! Prior to this week it was getting an average of
408 rounds per week put on it!
So I think again it has a lot to do with how the operator is using the brushes more than anything else and what I say is... "pay attention to what and how your doing it."
Later, Frank