Before:
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After:
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These pics are of a 6CM barrel that I brought back to life after believing it was completely dead after 2200rds... except it wasn't.
IMO you'll need a 10" chamber rod like this if you don't already have one:
Amazon product ASIN B00LCT9WCK
I use a nylon brush that is close to the OD of a loaded round (which for me with 6mm means using a .270"/7mm brush). I soak a patch with Bore Tech Eliminator, put it on the nylon brush's end, jam it in there, spin it around a bit, and just let it sit for a while. This is just to loosen the carbon up, sometimes it works great, and sometimes it barely does anything. I've heard Bore Tech C4 is even better for this and some guys swear by using Patch-Out and their Accelerator for this part too.
Then I come back with a patch (or 3) with a little Iosso on it and put that on the end of the oversized nylon brush, and spin it around in there for a bit, and usually, that's what really gets all the crap out of there and cleans it up.
For a long time, I believed all the fairy tales/myths out there about how one is going to ruin their barrels using bronze brushes and/or any abrasives like Iosso or JB bore paste... and most of that is straight-up bullshit. Using bronze/abrasives like a sane person, one quickly finds out that one would have to be a total idiot, or have set out to actually try and ruin a barrel on purpose, in order to do it over a barrel's life using a normal cleaning schedule. These days I use a fresh/brand-new bronze brush and a little Iosso every time I clean.
Use a borescope to monitor what you're up to and make sure you get any/all abrasives out of your barrel when you're done cleaning and you'll be just fine.
The barrel now has 2950rds on it and I've obviously ruined it using bronze brushes and Iosso... here's what 750 yards off a cattle gate/Shmedium bag looks like
:
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And as far as guys being afraid to use more aggressive techniques for cleaning, IDK what context Frank from Bartlein said what to use, or what not to use, and when... but with brushes at least, I know Greg from Bugholes has said this:
"I recommend you keep using your nylon brushes, that way you'll think your barrel is shot out sooner than it is, and I get the chance to sell you another barrel."
It seems a lot of precision shooters favor nylon bore brushes over bronze brushes. Why is this? What I've read suggests that nylon is less abrasive to the bore than bronze, but the way I see it just one copper jacketed bullet forced down the bore at 60,000 psi does more damage to the bore than...
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