Ogive question.

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by 4ked Horn, Apr 4, 2005.

  1. 4ked Horn

    4ked Horn Writers Guild

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    Wildcat bullets offers an 8, 10 and ULD ogive. Can someone tell me if these are standard designations like a thread pitch or a guage and where they come from and what .30 cal bullet has each of these ogives so I can look at an example of each of them on line?
     
  2. Jon A

    Jon A Well-Known Member

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    It basically describes the radius of curvature of the "nose" part of the bullet relative to the caliber. The higher the number, the larger the radius--the "flatter" the sides of the nose will be and (all else being equal) the longer the nose will be. It gets more complicated than that when you talk about secant ogives and offsets, but that should give you a basic idea. Here's a visual:

    [​IMG]

    Many Sierra MK's, Nosler BT/AB's are around a 6 caliber tangent ogive. A pretty good compromise between aerodynamics (high BC) and not being picky about the rifles throat, seating depth, etc to provide good accuracy.

    Many Hornadies (A-Max, Interbond, SST, "Spire Point"), Swift Sciroccos, old XBT's, etc use a more aggressive (~8-10 Caliber) Secant ogive. This is better aerodynamically (higher BC) but can be pickier about which rifle they shoot the best in, seating depth, etc.

    VLD, ULD, get even more aggressive in search of higher and higher BC's.

    That's very generalized, but hopefully it gives you a decent idea what the terms mean.
     
  3. 4ked Horn

    4ked Horn Writers Guild

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    Great graphic. Thanks.

    That helps solidify my choice on which ogive I will be putting on my first order of Wildcats.
     
  4. Mikecr

    Mikecr Well-Known Member

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    Were the Wildcats secant or tangent?
     
  5. bailey1474

    bailey1474 <strong>SPONSOR</strong>

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    Thanks. I had the same question, just hadn't asked it yet.
     
  6. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Mikecr,

    I believe both designs are used depending on bullet.

    Alot of the ULD bullets have an ogive between 10 and 15.

    Good Shooting!!

    Kirby Allen(50)
     
  7. 4ked Horn

    4ked Horn Writers Guild

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    [ QUOTE ]
    Were the Wildcats secant or tangent?

    [/ QUOTE ]

    I don't know. when I spoke with Richard on the phone he just used the numbers 8 10 and ULD.

    That would be a good next question for him, which one he uses.

    Next question for you guys- What is the difference between a secant and tangent ogive technically speaking?

    What effect do we see with one over the other practically speaking?
     
  8. 4ked Horn

    4ked Horn Writers Guild

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    From what I am putting together the ogive based on caliber would look something like this.

    [​IMG]

    We start with a 30 cal diameter. I then made 3 circles that were 6 8 and 10 times as big. If we use the section cut on a plane horizontal to the center of the caliber we end up with half of a bullet tip profile. I'm assuming this is a tangent ogive???

    If this is right then how come in the graphic above we see .5 for the ogive that is semicircle instead of 1. Are we dealing with the caliber radius or the diameter?
     
  9. Richard338

    Richard338 Well-Known Member

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    The number of calibers dictates the RADIUS of the circle describing the ogive. Thus a 10 caliber ogive for a .338 bullet would be described using a circle of RADIUS 3.380".
     
  10. Mysticplayer

    Mysticplayer Writers Guild

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    So does this mean that any calibre can be made to the same ogive thus BC? If this is true, then if we can figure out how to make them, you could have a 22cal bullet with a BC of 0.8 or whatever. That would have a ogive of 15 cals or so. Wouldn't be much more then 120gr so pretty easy to launch.

    No recoil with ballistics on par with the super big 338's. Very interesting...

    Jerry
     
  11. Alucard

    Alucard Well-Known Member

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    You would need one hell of a case to launch a 120gr .22 cal to get the velocity to reach the 0.8 BC. I think that there is a limit to BCs in every caliber in useable bullet weight range. But, truely, I don't know much about BCs and what not.
     
  12. 4ked Horn

    4ked Horn Writers Guild

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    [ QUOTE ]
    The number of calibers dictates the RADIUS of the circle describing the ogive. Thus a 10 caliber ogive for a .338 bullet would be described using a circle of RADIUS 3.380".

    [/ QUOTE ]

    So the numbers in my illustration should have been 3 4 and 5?
     
  13. 4ked Horn

    4ked Horn Writers Guild

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    [ QUOTE ]
    So does this mean that any calibre can be made to the same ogive thus BC? If this is true, then if we can figure out how to make them, you could have a 22cal bullet with a BC of 0.8 or whatever

    [/ QUOTE ]

    Among many other things BC is also a function of weight. I cant imagine a 42 gr .22 bullet approaching the BC of a normally shaped 168 grain .30 cal no matter how long the ogive is.
     
  14. Jon A

    Jon A Well-Known Member

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    [ QUOTE ]
    So does this mean that any calibre can be made to the same ogive thus BC? If this is true, then if we can figure out how to make them, you could have a 22cal bullet with a BC of 0.8 or whatever.

    [/ QUOTE ]
    Remember, of equal importance as the aerodynamic shape to the BC, is the bullet's sectional density.