Barrel contour education?

Discussion in 'General Rifle Discussion' started by Vincine, Feb 6, 2014.

  1. Vincine

    Vincine New Member

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    Okay, a standard hunting barrel is ‘light’ for walking around the woods, but it warms up and whips around more affecting accuracy. Not an issue for a few hunting shots.

    A heavy barrel doesn’t whip as much, holds accuracy better, but is best for lots repetitive shooting from a stationary position. Don’t even heavy barrels warm up and expand affecting the bullet/rifling contact?

    About fluting? Some sites say it is the increased surface area that promotes cooling. Some say it is the reduced barrel mass of the fluted areas between the inside and the outside that allow the barrel to cool faster.

    I looked at the Hart, Shillen, Krieger, McGowan, Lilja and Pac-Nor sites, but they don’t have a clear explanation of the pros & cons of all the various contours. Just that they can provide them.

    Can someone post a link to a comprehensive primer on the pros & cons of various barrel contours? All I find are sites with contradictory ‘facts’, ‘factoids’ and opinions, and I can’t tell which is which.
     
    Last edited: Feb 6, 2014
  2. nitestalker

    nitestalker New Member

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    I don't know of any sporting rifle barrel that is made for "High" heat use. Shooting any expensive custom cut barrel to high temperatures is like running you car without water. The damage will be internal. Throats and muzzles will be washed out regardless of the weight or contour.
    Heavy target barrels are cut to reduce harmonics and Ballistic warping of the action. Light sporter weight barrels or heavy barrels should always be timed fired to take advantage of bore uniformity and to preserve the integrity of the rifling. If you choose to raise the barrel heat by rapid fire you can expect much shorter barrel life regardless of contour.:)
     

  3. SSGN_Doc

    SSGN_Doc Well-Known Member

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    I know I have one rifle with a sporter weight barrel that does not seem to have any wander as it heats up. I don't know what kind of Viking magic they still do in Finnland, but that Sako stays put. Having a bore that is as straight as possible, as completely concentric as possible, that is rifled in a way that casues the least stress on the barrel, and is even then, stress relieved, may have something to do with it. Then that barrel is floated as well, and is attached to a very rigid, bedded action. I won't say that it is a "High" heat barrel. But I can shoot strings of 20 rounds of .30-06 with no evidence of the zero wandering in any direction, and the barrel is uncomfortably warm.

    Heavy barrels do add rigidity and will allow a "less perfect" barrel shoot more consistently for a longer period of time. A heavy barrel will heat more slowly, but they also cool more slowly as well.
     
  4. nitestalker

    nitestalker New Member

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    A less perfect barrel will be more accurate if it is heavier? What is a less perfect barrel? I am not clear on your post regarding a barrel with imperfections becoming more efficient with added weight? I really don't know how you would know the barrel would have had improved accuracy if it had been heavier? Educate me on this one?
     
  5. TLuker

    TLuker Active Member

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    Sorry but I don't know of any links and to be honest I think a lot of it is just opinion anyway? There is a science to rifles but there is also an art to it. Some things just work and some of it's just for confidence or because it sounds good. I've heard a lot of great reasons for fluting but I'm not sure if it makes a difference? Plus you put it all together in a rifle and there is no telling what you'll get.

    My first great hunting rifle was a sporterised (sp?) No. 4 Lee Enfield .303 British. Eventually I started tweaking it to improve the accuracy and latter on I bought a No. 1. They are very different rifles because one has a heavier barrel and there are subtle differences in the stock. I eventually bought the book The Complete Book on Lee Enfield Accurizing. I was amazed at all of the stuff in there on how to tweak each of the two rifles and the difference between them because of the barrels and stocks. And a lot of things in that guide didn't make a lot of sense. It was just stuff that people figured out after 100 years of tinkering with Lee Enfields.

    I think hunters and shooters just eventually figure out what works for each of us but we never quit tinkering or looking for that slight change to squeeze a little more accuracy out of our rifles. We also get certain things in our heads like thinking a certain contour barrel makes a difference. Just think of all the different opinions on breaking in a barrel or odd vs. even number of groves in the barrel. Maybe some of it works and maybe it doesn't? And I'm sure some of it does work for some people in certain situations. Maybe a certain contour works for a certain caliber with a certain action shooting a certain bullet? Someone hits on that combination and then believes that contour is the way to go for all calibers and actions when it isn't. There are just too many variables involved and much of it is still guessing. I'm sure barrel makers have heard it all before and they probably just quit questioning any of it and just sell us what we want.

    Just my .02 :)
     
  6. SSGN_Doc

    SSGN_Doc Well-Known Member

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    A heavier barrel will be more rigid, and may not wander as much from stresses in the barrel that cause the barrel to change shape as it heats up. A thinner barrel with the same imperfections in the metal or a bore that is off center would be more readily affected by the imperfections or flaws.

    As the barel is rifled by a rifling button or cutting hook it imparts some stress on the barrel metal. If the hook or button is worn, the stresses may be worse. Some manuufacturers stress releive the barrels by slowly heating them, then slowly freezing them and slowly rewarming them to relieve some of those stresses. Other manufacturers will just leave a barrel heavier instead of profiling it down to have the extra metal reenforce the barrel and reduce the affect of the stresses to the barrel around the bore. Kind of like splinting or applying a cast, except it is simply leaving more metal in place instead of adding material.
     
  7. nitestalker

    nitestalker New Member

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    Interesting. But I like the hammer forged barrels? How does that apply? Button rifling covers many types of rifling from Micro-groove to Ballard and everything in between. Barrel stress relive is used in all manner of barrels. There is as you know many ideas Pro and Con on how much Cryo or any other stress relive does for barrels. Fluting was considered a plus for heat dissipation and stress and harmonic improvement. We know now it was more cosmetic than practical.
    I think we should look closely at spring in the action at peak pressures and correct bedding. As you know twist rates throats and crown are determining factors. All of these experiments has brought rifle accuracy ahead by light years in the past 3 decades.:)
     
  8. SSGN_Doc

    SSGN_Doc Well-Known Member

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    Agree.

    Hammer forging seems to relieve stress by aligning molecules as the metal is compressed around the mandrel. But comparing inexpensive bull barrels, there is usually a reason, that some are inexpensive, and left in Bull configuration, and still on the affoardable side. They usually produce decent groups, but may not be on the high end of the competetive side. some manufacturers will use rifling buttons or hooks for longer periods and will accept more wear and chatter. Premium barrel manufacturers will change them out more often and the cost is partly reflected in the barrels. Chamber reamers and crowning tools as well.

    Whe I was having discussions with one of the reps from White Oak he was explaining how some barrels were abble to produce better accuracy with thinner profiles, and how a shorter, more rigid barrel could still produce great groups, in line with a longer heavier barrel, because rigidity was similar. Then he went on about metal stresses, stress relief, etc. So, I'm kind of going by memory from a phone conversation, and don't consider myself to be a true technical expert on the level as a manufacturer, machinist, and vendor for high end barrels. I did mention to him how I was impressed with my Sako when shooting it side by side with heavy barreled .22-250 Ruger 77, and how the sporter barrel seemd to hold it's own with the heavy barrel. I was looking into a match barrel for my AR for service rifle matches at the time.
     
  9. JonM

    JonM Moderator

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    Contour itself does a couple things.

    Heavier barrels are stiffer and tend to produce better groups.

    Light barrels great for hunting since they don't weigh much

    Fluting adds rigidity to a heavier barrel looks neat doesn't really do all that much. If not done right it can ruin barrel harmonics.

    Hammer forging is a means of producing a barrel without introducing linear stresses you fimd with drilling a bore by other methods.

    Chrome lining reduces damage done when firing multiple shots quickly. Its why military guns have it. If not done well it can really screw up a barrel.

    Cryo treatment. Freezes barrels for period of time relieving stresses from barrel creation.

    Air gauging. Checking uniformity of bore end to end.

    Button rifling method of use a button type bit pulled through a bore to create rifle.

    Microgroove is a very cheap method for producing low end barrels that shoot decent.

    The key to picking a good barrel is to know your purpose for owning it. What makes a great tack driver isn't often needed in a 100yard deer getter. That's why you see cheap barrels in things like ruger american or their m77 or a savage axis etc the intended use is getting a deer at 100 yards.

    I like hammer forged chrome lined barrels because they offer a nice combination of durability and accuracy.

    One thing to note, not all barrels from the same maker are the same... company A wants x ammount of barrels that all fall in y tolerance, company B wants the same barrels but will take them with y+-2...

    That's why there are a lot of gun makers and not so many barrel makers and even less barrel blank makers. This trend applies to companies like shilen krieger lilja white oak wilson arms etc. They too get their blanks from a supplier where the rules above apply.

    The problem is you need to sell the not so good barrels to someone... that's why there are high end guns and budget guns that have high end features.
     
  10. nitestalker

    nitestalker New Member

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    The concept behind a heavy barrel is founded in barrel making hundreds of years ago. A long heavy barrel was even better. In the modern age of barrel making technology these ideas are changing. Visit a serious Bench Rest competition and you will see the emerging new concept in accurate rifles. The larger, slang "Bull" barrels are dramatically down sizing. I do not know of anyone who is using "Chrome" lined target grade barrels. This has been proven to reduce velocity which is dependent on friction during the bullets lapse time in the barrel. This in turn can affect the ballistics of the bullets travel. Chrome lining serves to reduce friction in guns made for high rates of fire. The Japanese pioneered chrome lining of the Arisaka Rifles to speed production. This cut internal barrel finishing cost. :)

    I would add that Sako rifles have a reputation of out of the box accuracy. These rifles have cold hammer forged mandreled rifled barrels. There are different types of mandrel rifling as well. :)
     
    Last edited: Feb 9, 2014
  11. greydog

    greydog Member

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    I do not make barrels but I have installed many hundreds of them. I have worked with barrelmakers and spoken with others.
    The stress in barrels comes from two sources. The first source is the barrel steel itself. Although this steel is generally purchased as "stress-relieved" there is some variation between batches and, indeed, within the same batch. Many makers will stress reliev again after the blank is cut to length but before it is drilled or reamed.
    The second source of stress is that which is imparted during the manufacturing process. In general. this applies mostly to button rifled barrels wherein the rifling is cold swaged into the bore. For this reason, most manufacturers of button rifled barrels stress relieve after rifling but prior to contouring.
    Cryo treatment, the freezing of barrels by immersion in liquid nitrogen, has not been shown to accomplish anything with regards to stress relief. It does appear to improve machinability to a certain extent although there is still considerable debate on that issue as well.
    Hammer forged barrels are remarkably inert because the molecular structure is affected by the forging process. In addition, those barrels come out of the machine smokin' hot and are kind of self relieveing.
    Contour of the barrel is determined by the intended use of the rifle and the type. In some cases, rigidity is of paramount concern so the barrel is made heavy and not too long. In another case, it may be considered to be OK to sacrifice some rigidity in exchanged for the higher velocity produced by a longer barrel. A shorter barrel improves portabilty and quickens handling. A longer barrel makes the rifle hold steadier and smooths out the swing on running shots.
    How the rifle balances is greatly affected by the taper of the barrel. In oither words, not just the weight but where the weight is carried. If the weight is toward the muzzle, the rifle is muzzle heavy and will handle more slowly. If the weight is further back or between the hands, the rifle will be quicker handling although the two rifles may weigh exactly the same.
    A lighter barrel really will cool off more quickly than will a heavy one. It is good that this is so because it will also heat up much more quickly. So, in ten shots, the heavy barrel will have absorbed "x" number of btu's but this amount of heat will have raised the temperature of the barrel to a certain level. A lighter barrel will have absorb the same btu's but since there is less mass to heat, the temperature will be much higher.
    The extra weight will dampen vibrations and the heavy rifle will be less affected by recoil forces and the hold.
    Small variations in contour will have a greater effect on handling and appearance than they will on actual accuracy potential. The choice of a particular contour is, once again, dependent upon the intended purpose of the rifle and the handling chactaristics desired. If a rifle is to be used with a bipod, it probably doesn't matter since any balance has gone out the window anyway! GD