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 Precision Rifle Barrels... 
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Location: Monroe, Wa.
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Rifle barrels and Harmonics
This is another ‘article’ I wanted to post because I get asked about it often. It is not meant to be comprehensive, but to lay down some basics for people to understand what some terminology means, and dispel some rumors about rifle barrels. Please feel free to ask questions, or post what you have learned that may agree/disagree with what I have posted.
Since the barrel is really the ‘heart’ of a rifle, it is important to understand what factors affect it, and what you can do to get what you need out of your system.

The length argument
I’ve heard people try to argue that longer barrels are more accurate, and this is scientifically not possible. The only advantage to a longer barrel, given the same contour, is potential velocity increase based on the ability to burn more powder before the bullet is released. Barrel length has nothing to do with inherent accuracy. However, it does have to do with rigidity.
Whip
When a round is fired down a barrel, the barrel will flex and return in a whip-like motion. This can actually be seen in high speed video. This flex is commonly referred to as whip, and is the basis for the discussion of harmonics. Given that this motion is occurring when the rifle is fired, anything that makes that motion inconsistent is going to reduce accuracy. Furthermore, the less rigid a barrel is, the more pronounced the whipping motion, and the greater an effect a change is going to have on it.
Since the bullet is being released from the barrel at some point in the whipping motion, we want to control that as much as possible. Theoretically, if we could release the bullet at the same spot in the motion every time, we would have almost perfect accuracy, putting the bullets through the same hole every time. Unfortunately we have several variables working against us, the main one being the consistency of the ammunition we fire through the barrel. Deviations in velocity will produce deviations in the whipping motion, though they may range from small to large. This happens because the bullet is released from the tip of the barrel at a very slightly different point in the movement, because the velocity is different. Tuning a load to a barrel is simply the process of finding the ‘nodes’ or powder ranges, where the change in point of impact is the least affected by slight changes in velocity. Further explanation of this reasoning or process can be provided….
Fluting
This has been beaten to death, but I still hear people asking about fluted barrels being ‘more’ rigid than their unfluted counterparts. That’s ridiculous. It’s actually quite simple, when you remove material, you lose weight and rigidity. A fluted barrel of a given diameter will be less rigid than an unfluted barrel of the same diameter. However, and this is where the confusion comes from, a fluted barrel of a given weight will be very slightly more rigid than and unfluted one of the same weight. It will also cool a little bit faster, depending on how much surface area is gained by the flutes.
Barrel break-in/cleaning
This is another one that has been beaten to death, and the first thing I should point out is that I am not a benchrest shooter. The benchrest crowd have a developed a routine that works for them, and I understand their logic and their methods. What I am about to say does not make their methods wrong, just different.
Barrel break-in only applies to a very few conditions, such as a factory barrel that has not been lapped well, and may have a rough throat area from the chambering process. There are a few methods to deal with these barrels, but you’re fighting an uphill battle. Some of the methods I’ve heard recommended are; Tubbs Final Finish Rounds, which have an abrasive on the bullets to smooth the throat and bore, pastes such as JB, used as a lapping compound of sorts, or shooting and cleaning in a routine to ‘smooth’ the bore. If bought a rifle with a barrel that bad, it would either be for hunting, or it would go back to the manufacturer. I shouldn’t have to finish manufacturing the firearm I was intending to buy. Most modern day barrels are lapped after manufacturing, which should alleviate most of the issues from above. Quality barrels, like a Kreiger or Rock barrel, are lapped to a fine finish before they leave the manufacturer and the idea of Joe Blow running his cleaning rod down it a hundred times makes the hair on the back of my neck stand up.
Here’s the thing… when you start shooting rounds through your rifle, the copper leaves behind a thin coating on the bore. After a few rounds this coating stabilizes, burnishes, and tends to stay fairly consistent for hundreds of rounds. If you clean your barrel to the steel after shooting, your rifle will need to rebuild that layer to be back where it was. Depending on the barrel, this may cause inconsistency, or it may not even be noticeable. Typically, if I feel the need to clean my rifle, I only knock the carbon out of the bore every couple hundred rounds. Cleaning the copper out would be done if; the rifle wasn’t shooting as well as before, I’m doing some new load development ( in which case I would foul the barrel before I shot for record) or I shot over 1000 rounds through it…. Then I might just clean it for good measure, but again I would shoot it to lay down a new layer of copper before trusting it. Furthermore, when you clean your barrel to the steel, you expose it directly to the forces of the bullet and the explosion pushing it down the barrel. The temperature of the expanding gases right behind the bullet can exceed 4000 degrees, if you expose your throat to that often enough, you will shorten the lifespan of your barrel considerably. Ask a benchrest shooter how long their barrels last…
Final note: Some of this is hotly debated, but this is what I have learned, and what makes the most sense to me. Also, many factors can be compensated for, such as mapping the shift of a barrel as it heats up, or immediately after it has been cleaned. It comes down to what you need out of the system, and what you’re willing to do for a given result.

Let the questions, comments, critiques begin!

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Mon Jul 23, 2012 8:49 pm
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What is the final word on moly when reloading?

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Mon Jul 23, 2012 8:54 pm
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Actually the word right now is that moly is old news and Hexagonal Boron Nitride is the new cool thing.

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Mon Jul 23, 2012 9:00 pm
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Whats it got on moly?

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Mon Jul 23, 2012 9:14 pm
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fact......most any rifle i pick up is more accurate than i am. :thumbsup2: so i try not to stress about it. that is all i know.

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Mon Jul 23, 2012 10:35 pm
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So if you only clean the carbon out every 200 rounds, do you put oil down the bore after your done shooting for the day? We live in a damp climate. can that fouling attract moisture?


Mon Jul 23, 2012 10:40 pm
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tomy salami wrote:
Whats it got on moly?



Works as good and doesn't leave all the shit behind.

On that note, shooters are like racers. If a stock car racer waxed his hood before every race and won all the time, pretty soon everyone on the track would be waxing their hood.

Ditto with shooters. If someone was to dip his bullets in chicken feces, and he won every match, the next thing you know the shooting line would smell like the pens at Tyson's.

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Tue Jul 24, 2012 8:19 am
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deadshot2 wrote:
tomy salami wrote:
Whats it got on moly?



Works as good and doesn't leave all the shit behind.

On that note, shooters are like racers. If a stock car racer waxed his hood before every race and won all the time, pretty soon everyone on the track would be waxing their hood.

Ditto with shooters. If someone was to dip his bullets in chicken feces, and he won every match, the next thing you know the shooting line would smell like the pens at Tyson's.



:ROFLMAO: .... Truth!

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Wed Jul 25, 2012 10:30 am
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platz wrote:
So if you only clean the carbon out every 200 rounds, do you put oil down the bore after your done shooting for the day? We live in a damp climate. can that fouling attract moisture?



I only put oil down the bore if I don't think I'm going to be shooting for at least a month. I might actually clean it as well if I am that sure. Most of my rifles have stainless barrels, and I try not to let them sit unfired for too long, but sometimes they do. Oil in the barrel is one way to help, but I try to avoid it. If you do use oil in your barrel, make sure you use a solvent or lots of patches to make sure it's all gone before you fire. If there's oil in your bore when you fire, the hydraulic action can ruin a barrel.
The right answer is a dehumidifier, which I need to get around to..

The moly/hbn thing has yet to draw my interest. I've heard the supposed advantages and disadvantages and I'm not convinced that it's worth the trouble. There are already enough variables with ammunition and reloading, I don't need any more. My goal is to shoot, I'll let the benchrest guys and experimental types figure out the new products, and when the data is solid and proven, I'll consider it.

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Last edited by Samurai on Thu Jul 26, 2012 7:50 am, edited 1 time in total.



Wed Jul 25, 2012 8:04 pm
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Quote:
The right answer is a humidifier, which I need to get around to..


I believe you meant DeHumidifier.
I use one in my gun room to keep the humidity around 38-42%.

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Thu Jul 26, 2012 7:43 am
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Thanks for catching that, kind of an important difference...

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Thu Jul 26, 2012 7:52 am
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So if you shoot often enough you just bring your rifle home and stick in a safe and not bother cleaning it? I usually run a bore snake through mine with a little CLP through after a range trip, approx 30-40 rounds. Is this a bad thing that I'm knocking the carbon out of it that often?

as for what seems like a short range trip, I'm still getting used to the recoil, I recently switch to left handed shooting being left eye dominant.


Fri Jul 27, 2012 8:39 pm
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Yup, I just stick it back in the safe. And the only reason I clean in less than 500 rounds is that I shoot almost exclusively suppressed, so the crown gets a lot of gunk built up on it.

Knocking carbon out won't hurt anything, as long as proper tools are used to clean, it just isn't necessary.

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Sat Jul 28, 2012 10:03 am
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I typically don't do a thorough cleaning since I don't have a one piece rod and don't want to damage the barrel with the sectioned cleaning rods.


Sat Jul 28, 2012 10:09 am
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boostless wrote:
I typically don't do a thorough cleaning since I don't have a one piece rod and don't want to damage the barrel with the sectioned cleaning rods.


If you're talking sectioned rods like the GI cleaning kit, just take some time and wrap each rod section with electrical tape. Be meticulous and make sure the tape is wrapped in a smooth spiral with the edges flush to each other. Even if you have a slight gap at the "joints", the tape will still keep the metal from contacting the barrel surface. A good "watch TV project". For those who play "outside the wire", the tape on the rods will also keep the kit from rattling as much.

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Sat Jul 28, 2012 12:49 pm
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