Been working on a new : HP bullets for target shooting!

Discussion in 'Cast Bullet Shooting & Testing' started by JWFilips, Aug 8, 2017.

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  1. Intheshop

    Intheshop Well-Known Member

    Stay with me here....yes it's a tangent.

    The discussion,which often turns heated,in physics is like two finishers(spray guns) who can't agree on this or that process technique.One of my boys got about as far up the former ladder as he wanted($$$ think tanks).To which it was described to me,that changing one small part of the discussion,effects the outcome.

    I saw the same thing in discussions (arguments) on finishing.

    The above is why,in my pea brain....that not only can you get to the same location by two different routes,but also by two different methods.Quit thinking right/wrong,white black.The complexity is in the difference.
     
  2. Eutectic

    Eutectic Active Member

    Fluted barrels remain in my 'cosmetic' corner until I see some direct one against the other comparisons. Stress relieving can be a friend or an enemy...

    2400 never gets a hot primer in my loads.... But it's a good discussion item..... It's very close sister from the same womb..... One Alliant 410 sometimes does like it hot! .41 Mag uses the last of my 2400 supply.... and then only with a Federal 150.

    Intheshop explains some of the complexities above about how 'odd in our logic' for some change may very well get us to our target (and closer together too!) It's not only bullet lube that can be complex to achieve certain results. It's the whole ball of wax! (pun intended)

    "How quickly the bullet goes to sleep"....

    But if you want a 'spirited' discussion; change the 'How quickly' to 'Why does' in Intheshop's quote line right above...

    Pete
     
  3. S Mac

    S Mac Active Member

    In my mind this is the yaw dampening Ian referenced earlier. Is this a correct assumption?
     
  4. KeithB

    KeithB Active Member

    Removing material anywhere from the outside of a cylinder NEVER makes it more rigid or stiff. Take two barrels of the same outside diameter, flute one of them. The fluted barrel has more surface area and weighs less but it is less rigid or stiff. If you want a fluted barrel to be as stiff as an unfluted barrel you have to start with a larger diameter barrel. The fluting can reduce the weight to be the same or less than an unfluted barrel, and you will definitely have more surface area.

    I am not much of a rifle shooter, I can't comment on performance of fluted versus unfluted barrels, but as far as the stiffness question it's just basic physics.
     
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  5. Ian

    Ian Well-Known Member

    Yes. If the stability factor is marginal it can take over 100 yards of bullet travel before the bullet holes become round and groups start to group. Seen it happen more than once. Typically, we read that a bullet with a good stability factor will cease yawing by 5,000 caliber lengths of travel past the muzzle. So 10-30 yards. Hollow-pointing bullets should reduce this distance by increasing the stability factor, though I've never tested it. I think this is what Jim is trying to accomplish through his tests, to see if the hypothesis holds up.
     
  6. RBHarter

    RBHarter Well-Known Member

    Coming from aviation I would disagree about straight line load bearing flex resistance of a ribbed or fluted tube vs it's straight wall counter part . The catch of course is weight management and cost . In a bbl by dia vs cal/cartridge you reach some point of return that is to small to be measured . Making the presumption of 3 dia being an apex point . A 25 cal would need a .771 dia . A bbl tooled as close to identical at 1.0" is going to be more rigid but with effectively vertically radial full length flutes that match the weight/mass of the .771 straight taper the fluted bbl will be more rigid .
    The 2nd layer of mechanics is where the above gets sideways because of torque and pressures . Spiral flutes that match the rifle twist may or may not negate that .
    Any time surface area is added to a tube without reducing the the total material below minimum strength will be more rigid . Symetrically of course . This is why 2 2×3s flat and 9" of 1/2" plywood can be spanned 12' and a 2×12 in solid lumber matches it even though the volume of mat'l doesn't match .

    As a rule fluting however is not used as a tool for rigid structure in fire arms . It is used to increase surface for cooling which is a questionable use , weight saving and aesthetics .
     
  7. Ian

    Ian Well-Known Member

    Barrel flutes have the same effect as putting googly eyes on crankbait: To catch fishermen, not fish.
     
  8. Intheshop

    Intheshop Well-Known Member

    OK,dang it.....should NOT have said barrel fluting.I was thinking about the bullet itself.The rifeling imparts,albeit swaged...flutes (or whatever you want to call them)to the outside of the bullet.Which only happens after a trip through the barrel.

    And don't know diddly about paper patching.And am not talking about muzzle loaded bullets.It's the idea that flutes can add integrity.The HP is helping that process.

    Beading and flutes are routinely added to sheet metal to stiffen it.So if the receiver or magazine is stamped,then yes...fluteing is used on firearms.
     
  9. Ian

    Ian Well-Known Member

    Rifling on cast bullets does diddly. Rifling engraves on jacketed bullets makes stress points that split longitudinally upon impact, like a banana peel. Flutes and beading only add rigidity in a relative manner (not the best analog to rifle barrel flutes where the barrel is a lot thicker than the flute depth) and only have any effect below the elastic limit of the material.

    Bullets are plastique, ergo sed hoc non est.
     
  10. Intheshop

    Intheshop Well-Known Member

    Think of spiral dust collector tubing,it ain't on there for looks.Same as a drainage culvert pipe.Both hollow.
     
  11. Brad

    Brad Moderator Staff Member

    Look at wall thickness. Drainage pipe needs the corrigation to make up for thin walls. It is also made of a relatively flexible material.
    A barrel has thick walls by comparison. They are also made of a rigid material compared to drainage pipe.
    Look at PVC pipe, no corrigation due to stiffer material and thick enough walls.
    Apples to orange.
     
  12. Intheshop

    Intheshop Well-Known Member

    Yup,made a mistake.....never mention barrel flutes in the abstract,haha.
     
  13. Intheshop

    Intheshop Well-Known Member

    The next fluted pilaster we mill,I will test it before and after.Same board....same weight hanging out on the end....will measure the before and after deflection.Don't know,anyone want to make a wager?
     
  14. Intheshop

    Intheshop Well-Known Member

    Two more....NOT barrel examples of fluting which stirs the natives...

    The sole of a wood plane...AND, this one is extremely weird because I was dinking around with it this very morning.A pre war stationary sander we're setting up as a metal,belt grinder.The platen is fluted.

    Most think its about,only reducing friction,on both accounts.But,they tend to stay flatter...longer.Meaning,they're stiffer once the flutes are ground in.

    Pretty nice sander....nasty little bugger though.
     
  15. Brad

    Brad Moderator Staff Member

    In the abstract, fluting may increase stiffness. Rifling marks on the sides of a bullet may increase stiffness.
    My point is that it is a matter of degree.
    If fluting makes a barrel 1% stiffer is it relevant? Can a direct impact on accuracy be found/measured? I don't know.
    Bill, as an engineer can you calculate how much stiffness can be changed by fluting a barrel of the same bore size and diameter? How increase in barrel diameter would it take to see the same stiffness increase?
     
  16. smokeywolf

    smokeywolf Well-Known Member

    Keith said it better than I, but, Mass = rigidity.

    There's a reason long range shooters prefer ("bull") heavy barrels.
    Not so sure that it's an advantage to having a barrel heat up more quickly or cool down more quickly. Less mass means more susceptibility to differences or changes in ambient temps.
     
  17. Intheshop

    Intheshop Well-Known Member

    Here's another anomaly that would love a physicist/mathematician try to explain(and I know a PHD,haha).....

    I can,and do...routinely grind stock off bow limbs and they pick up speed.Same arrow,same string,same everything.And it isn't the physical weight of the limb,although that is part of the equation.The poundage goes DOWN,and it's picking UP speed.

    I can explain it,but won't.The point of my rambling is you can't always assume things or try to assign numbers to it.
     
  18. S Mac

    S Mac Active Member

    I'm no mathematician but I would say in your example the limbs are lighter, less initeria to overcome, therefore quicker.
     
  19. Ian

    Ian Well-Known Member

    Exactly, a matter of degree and relativity. Convoluted tubing of any kind is designed to give maximum crush strength at the lowest possible weight and and lowest possible material consumption. It also is the ideal choice where it needs to bend and deflect without deforming in a way that would compromise the circular cross section and cause a radial collapse. Corrugated roofing materials, and cardboard, are a lot more stiff than flat material, obviously, and that might be a better analog for a fluted rifle barrel. 1960s VW wheel bolts had hemispherical pockets in the center, presumably to add strength against the corners of the flats flowing outward and rounding off....which gets us into some deep subjects of force vectors encountering the surfaces of solids and stress analysis.

    Basically saying the same thing.

    Now we're on a slightly different but related subject...vibration. Mass = rigidity because mass absorbs heat of vibration and just generally takes more force to move quickly. Same deal with bench rifles, you want barrel harmonics to be minimal, hence mass. Most shot strings are five rounds with a few sighters, so heat-sink quality is a secondary consideration, though still an advantage when barrel mirage and heat deflection/bore-diameter change.

    Now, back to the corrugated cardboard or sheet metal examples and stiffness...maybe barrel flutes can add resistance to deflection without necessarily adding strength. Still, I think they're more eye candy than anything, if they added a significant advantage the F-class people would use them.
     
  20. KeithB

    KeithB Active Member

    Flexural rigidity is a function of how much material you have and how far away it is from the neutral axis. That's why I- and H-beams have most of their mass in the flanges instead of the web. That's why a hollow tube of a given weight per length is more rigid than a solid round bar with the same weight per length. The rigidity goes up by the distance away from the neutral axis to the 3rd power. In other words, make the distance away from the center twice as great and the rigidity increases by a factor of 8.

    Corrugated materials have a lot of their mass at some distance away from the neutral axis compared to a flat piece of sheet metal or paper/cardboard of the same thickness, ergo they are more rigid. That's why built-up wood beams can be rigid enough to span impressive distances with acceptable deflections yet be a lot lighter than a solid beam of the same cross section - a lot of the mass is away from the neutral axis.

    I will stick with my assertion that fluting a barrel of a given size reduces the rigidity, to get equal rigidity you must use a larger diameter barrel to start with. And I will take the bet that a fluted column will deflect more than an unfluted column of the same OD and ID.
     
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