temperature /speed chart ?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Guest, Aug 7, 2002.

  1. Guest

    Guest Guest

    Does anybody know where I can find a chart that will tell me what the new muzzle velocity will be based on a temperature change?
     
  2. daveosok

    daveosok Guest

    I have seen on average with my rifle and handloads a 10 to 12 fps gain per ten degrees. Since this is a variable its impossible to tell you what you may get as a diff but 10 fps is a good all around figure with the rifles I have loaded for and tested.
     
  3. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Any decent ballistic program will have that feature in it.

    Simply run a chart for every ten degrees and keep it in a folder in your backpack or vehical.

    The big change will be from 40 or 50 degrees one day and then 80 or 90 the next, which does happen from time to time.

    DC
     
  4. *WyoWhisper*

    *WyoWhisper* Guest

    Unless you live here in Wyo where the temp. swing can be 30 - 40 degrees depending on altitude and time of day.. drives you nuts....

    Thats why I am looking for a hand held comp. that can have a ballistics program loaded into it..!!
     
  5. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Hello Ric

    The "Major" changes are the ones to be extra concerned about.
    A change of only 10 degrees and 1000 feet elevation is not a major concern. As a matter of fact, a temperature change of 50 degrees really don't change the MOA that much in my 338/416 at 1000 yards. It is 15.5MOA to 15.9MOA at 1000 yards. 4/10ths of a MOA is only 4" at 1000 yards. Not really enough for me to miss the target/animal I am after.

    Now if you program a 40 or 50 degree change the "same time" you rise in elevation from 1000 feet to 7000 or 8000 feet, now you have a major change. This is a 17" difference with both temperature changes and alltitude changes combined "in my rifle".

    If the temperature and altitude is not "major", the trajectory is not effected "to an extreme".

    A hand held computer is available for this if you want to carry it.

    I trust my rangefinder, my rifle and my spotter for this change and take a spotter shot 100 or 200 yards away from the animal first, make my correction and then swing back on him for the kill. This procedure is done when the ranges are extreme.
    Most times at only 1000 yards I go right for him the first shot.

    Later
    DC
     
  6. RBrowning

    RBrowning Well-Known Member

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    Darryl,
    Doesn't a temp change throw a double whammy on you? Doesn't it first effect the burn rate of most powders therfore the MV that you will have to begin with, then it changes the air density to change drag?
    Rick
     
  7. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Hello
    At only 1000 yards it seems to matter ONLY when a drastic change is seen in temperature AND altitude.

    It dosen't seem to make that big of a difference when in the hunting fields and what I have noticed at the 1000 yard mark. Over 1000 yards and out to 2000 yards it is noticable.

    Most people carry their ammo in the pocket of their down clothing in the winter to keep it a bit warmer and keep them in an ice chest, chilled down when it's 90 plus. Is it really needed? Normally the ammo temp is the same as the outside air if you have your ammo in a box and outside with the rifle.
    I think if your shooting HOT winter time loads, you better chill them down when you take that SAME ammo into 90 degree heat.

    The computer ballistics program is figuring a temperature of the outside air and to an extent the same ammo temperature.

    For me, I have not really seen a BIG change within 1000 yards unless the temperature changed by 40 or 50 degrees and also when we combined that with a new altitude location of several 1000 feet.

    If your talking about the near same temperature and just a slight elevation change, theres not much change in trajectory. It takes a drastic change in most cases to see a BIG difference.

    This has been my experiance.

    DC

    [ 08-08-2002: Message edited by: Darryl Cassel ]
     
  8. *WyoWhisper*

    *WyoWhisper* Guest

    Howdy DC,

    Well I unfortunatly do have major altitude and temp. changes thoughout my hunting day. I could start at 5000 at 55 degrees and get to 10,000 and have 30 degrees easily ...

    I'd be curious what the name of the handheld is that I could load a ballistics software program into... hmmm thinking again....
     
  9. Darryl Cassel

    Darryl Cassel Well-Known Member

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    Ric

    Heres the variance of the 30 degree to 55 degree change of temperature along with the 5000 feet elevation up to 10000 feet change.

    At 50 degrees and 5000 feet elevation at 1000 yards, I would need 16.1 MOA in my 338/416 Rigby

    At 30 Degrees and 10,000 feet elevation at 1000 yards, I would need 15.4 MOA to cover the same distance.

    We are talking about 7/10 MOA or 7" at 1000 yards.

    Not really a MAJOR concern if your spotting for someone or have a spotter for you.

    This would change though if someone were shooting a bullet of low BC as compared to what mine does.

    As for the ballsitics program.
    I was refering to the small computers that are available and not to a tiny little hand held. Some of the very small laps that you can hardly use the small keys would work for you.

    Later
    DC
     
  10. Brent

    Brent Well-Known Member

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    WW,
    The Horus Vision has a Handspring Visor and a chip loaded with a program capable of what we need, including angle changes, wind, BP, Temp etc. $240.00 for everything. I talked to Dick B. over there and this is the model we need for use in the field he says. Used with any other palm device, the program is lost when the batteries go dead. It then needs to be reloaded while connected to a laptop or desktop PC containing it too. This is not necessary with the Handspring Visor unit, it contains the info on the chip so new batteries just need to be installed then turned back on.

    I'll be getting one in a couple weeks and will let everyone know how it works out.

    Demo

    HandSpring Visor With Module and program
     
  11. *WyoWhisper*

    *WyoWhisper* Guest

    I will be awaiting your results anxiously!!!!!
     
  12. RBrowning

    RBrowning Well-Known Member

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    Has anyone checked out the Exbal calculator from Perry Systems? http://www.perry-systems.com/palm.htm

    They say that they can accomodate the enviromental changes from sight-in at one location and climate to shooting at another. I ordered the PC version but they also have a PalmPilot version.

    [ 08-09-2002: Message edited by: RBrowning ]
     
  13. texas

    texas Well-Known Member

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    Darryl what program are you running and where can we get one?