re: Hornady Barrel Cleaning, Part 2. Updated on page 2

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The volume of the barrel decreases a whole lot for a very small decrease in diameter. Thats going to increase the peak pressure, cause peak pressure to happen sooner, and increase pressure for the whole event.

I can see how that would get dangerous eventually. Id like a clearer explanation of how it would degrade accuracy

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Change in pressure is definitely going to affect velocity. I absolutely see that. My first few round or two after a cleaning are 30-50 fps slower than typical. Once I get some fouling, speed levels off back up at my known velocity. And consistent speed is necessary for accuracy at distance. Additionally, I have a hand load developed for my gun. Each individual gun tends to like certain velocities for certain bullets. That's a whole discussion Im only vaguely familiar with, but think barrel harmonics, etc.. Spent a lot of time tweaking variables to get consistent velocity and tight groups. Dirty barrel throwing my speeds up 10 fps could get me out of that sweet spot and I grow from 1/2 MOA to 1 MOA. This is on a target rifle and although 1 MOA is not inaccurate in the grand scheme, it's a huge loss in accuracy compared to what the gun is capable of.

I'm sure this video series is geared towards those who are really fascinated by optimizing their loads and accuracy. Will a dirty barrel make you miss a deer broadside at 100 yards....I seriously doubt it can get that bad. But when I go down the rabbit hole of chasing velocity standard deviations of less than 5 fps, and groups in the .5xx MOA or better, it plays a factor. With my 6GT, it's at about 150 rounds, but I'll often clean before I get there. Haven't figured it out on my 6.5 PRC build because still developing a load and breaking in the barrel. Those are the only guns I hold to that standard, because that's what they were bought for.

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What kind of damage? What cleaning methods were done poorly?

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Main thing I would worry about is metallic brushes and multi piece cleaning rods. Where the rods screw together, you get a square shoulder. When pulling back and forth, you could create smalls scratches, especially at the crown. A knick on the crown could have pretty large implications on accuracy. Apparently abrasive fluids could also create some damage to the inside of the barrel, but I'm never super concerned about that. Just use decen solvents and clean them out when done.

Your process is pretty similar to what I'm currently doing, but I use Wipe Out foaming solvent in the early stages to minimize brushing w/ the cleaning rod. Once it's pretty clean w/ Wipe Out, I turn to bronze bore brush (to break up any residual hard carbon deposits), patches and solvents (Hoppe's #9 and Butch's). I don't use copper solvents unless there's a lot of copper staining. I very rarely use abrasive pastes like JB.

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Then a bunch of dry patches right there, because a lubed up chamber ends up leading towards heavy bolt lifts for a few rounds.

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Good point. Oil or solvent in the chamber can cause a spike in chamber pressures. This has happened to me a few times when I forgot to dry out the chamber.

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Does the calculation for the volume of the barrel include the barrel length or is it based on the diameter only?

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Yes, the length matters for the volume. Pi squared times radius times length.

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clearer explanation of why it increases (chamber?) pressure.

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I get this part. Less room for powder to expand = higher pressure.

Same reason thick brass will overpressure at lower powder weight than thin brass. Less room to expand = more pressure.

Its a closed system till the bullet leaves the barrel. As the bullet moves forward, the total volume of the system increases. The powder is burning, creating gas and pressure. A given amount of powder is going to produce a given amount of gas. The less room there is for that gas, the more pressure there will be.

Hornady Barrel Cleaning Video, Part 2

Ok guys, I took one for the team and listened to part 2 of Hornady’s barrel cleaning video. As a bonus I also listened to “Barrel Break-Ins and Barrel Cleaning Voodoo Rituals Destroy Barrels” from Military Arms Channel. Since it was a long walk I even had time to listen to a little Boz Scaggs at the end. Anyway, the main things I remember from Hornady:
-They said some products work better than others. They didn’t mention any products to avoid. The only products they mentioned they use were primarily Bore Tech Eliminator. They also use some “Wipe Out” and “Patch Out.” They favor letting the solvent clean and keeping the barrel strokes to a minimum. They like to let the bore solvent sit in the bore a while. They don’t plug the bore, saying many solvents need to be in contact w/ the air to work best.
-Hornady has 500 pressure/veocity barrels.
-Any barrel that’s been used in the Hornady lab gets cleaned at the end of the shift so they may clean 15-30 barrels/12 hr shift.
-I didn’t hear them mention recommending any of the copper cleaning solvents such as Sweet’s. One guy did say he got a 6.5 PRC 140 gr bullet stuck in a bore once. He couldn’t knock it out w/ a rod. He let some copper cleaning solvent sit in the barrel in contact w/ the bullet. After sitting for a period of time he was able to knock the bullet out w/ a wooden dowel. The main thing they said about the copper cleaning solvents/ammonia solvents was to oil the bore up really well afterwards.
-Don’t leave any solvent/oil in the chamber after cleaning. It doesn’t actually increase chamber pressure, but increases perceived pressure by increasing thrust on the bolt and frequently blowing primers.
-Don’t attempt to clean a “carbon ring” unless you’ve seen it w/ a bore scope. They mentioned the Chinese knock off bore scope from Amazon. I’ve got one but haven’t used it yet. If trying to clean a carbon ring, first soften the carbon ring by letting it soak in Bore-Tech Chameleon. If that doesn’t work, try JB’s Bore Paste or Iosso Bore Paste. These are listed by increasing abrasiveness. One of them once used diamond rouge on a barrel that had a carbon ring after 40 rounds that was going to ruin the new barrel. At the time, a new barrel would’ve cost $800-1000. It worked, but he doesn’t recommend it.
-The bore guides they mentioned using are made by Possum Hollow.
-They again endorsed using a personal reference load having known pressure, velocity and accuracy in your gun. They again mentioned a bump in velocity (as small as 50 fps), possibly a drop in velocity or drop in accuracy of the reference could indicate the barrel needs to be cleaned.
-While they mentioned using nylon brushes a little, I didn’t hear them say anything about using copper, stainless or tornado brushes.
-They don’t think cleaning a barrel to “bare steel” will be of benefit to anyone except a special group like benchrest shooters.
-When breaking in a new barrel, they don’t practice special methods like “shoot one, clean one” etc. They shoot a 20 rounds or so and start testing. Usually the barrel will settle ini after 10-15 rounds.
Sorry to be so long-winded, but it was a long video.

"Barrel Break-Ins and Cleaning Voodoo Rituals Destroy Barrels". I really liked this video and it's only 17 min long. He also uses Bore-Tech Eliminator, lots of patches and not much brushing. He also uses ony nylon brushes.
Hornady Barrel Cleaning, Part 2

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When breaking in a new barrel, they don’t practice special methods like “shoot one, clean one” etc. They shoot a 20 rounds or so and start testing. Usually the barrel will settle ini after 10-15 rounds.

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There's a few well-known people out there that dispel the need for a break in method. Erik Cortina for instance has definitely talked about it. I think he reached out to Bartlein Barrels and asked where their break-in method came from and they basically told him there's no real reasoning, customers just expect a recommendation, so they provided one. I personally tend to get new brass with a new rifle and use that first 100 or so rounds to fire form the brass and get the barrel to settle in. That's usually two range sessions and I'll clean after both and then really start load development and only clean when I see accuracy or velocity shift.

The rifles I’ve broken in seem much easier to clean for the years.