Velocity and barrel length

Discussion in 'Ammunition & Reloading' started by Mouser, Sep 13, 2019.

  1. Mouser

    Mouser Well-Known Member

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    In loading pistol caliber rounds, specifically 45LC and mild 44mag; how much velocity jump can be expected moving from a 7.5" bbl to a 20" rifle bbl...I don't have a chrono so I know it will be Kentucky windage and I'm thinking it will be maybe 100-200 fps depending on load...say 45 LC loaded with 250gr bullet to 900fps for example in a 7.5" bbl
     
  2. JimRau

    JimRau Well-Known Member Supporter

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    I have not been exposed to those particular calibers, but I can tell you that my experience with the 357 Mag going from a 4 in bbl to a 16 in bbl I saw increases of 400 to 600 fps.
     
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  3. BillM

    BillM Well-Known Member Supporter

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    "It depends". You will see the biggest increase with relatively slow powders.
    With a fast powder you could very well see a decrease---powder is burned up in
    the first few inches, and after that friction slows the bullet. With chronographs
    available around $100, it might be time to get one?
     
  4. Double20

    Double20 Active Member

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    I reload for .44 magnum and have a Henry Big Boy with 20" barrel. The load I settled on was a 240 grain bullet over 23 grains of H110. According to Hodgdon's website, this will give me 1750 fps out of a 20" barrel. That is found under their rifle data. If you go to their pistol data, the same load is listed there and the test barrel is 8.275" instead of 20" like the rifle data. The velocity of the same load in the shorter barrel is listed at 1413 fps. A difference of 337 fps. You can use their site to make comparisons between different loads with different powders and bullet weights. Their pistol data is only for 8.275" barrel instead of your 7.5" barrel but it should give you a general idea.

    **EDIT** I just checked and they don't list rifle data for 45 Colt, just 44 Magnum.
     
    Last edited: Sep 13, 2019
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  5. SGWGunsmith

    SGWGunsmith Well-Known Member Supporter

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    Some don't even disclose how they arrived at the data they mention. That's the main reason that I wanted a chronograph so that I could measure the velocities for my "out-west" hunting and prairie dog blasting forays.:

    [​IMG]

    Then I can actually measure velocity at 10 feet from the muzzle with 'this' or 'that' load and bullet weight and get a pretty accurate calculation at 300 to 400 yards when "snuffing out" prairie dogs.
    My longest shot ever on a pronghorn antelope was a measured 387 yards with a range finder while he was standing and lookin' at me. With that distance information I knew where to place my crosshairs so the 100 grain 6mm bullet could do its job. Pretty dang close to where I was aiming as the bullet struck just behind the shoulder but a little high. DRT.
     
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  6. RJF22553

    RJF22553 Well-Known Member

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    Barrel length has an important impact on PCC. Some powder charges are designed for short barrels (fast-burning), others for a longer barrel (slow-burning). My common calibers (9mm pistols and a CX4 carbine) will use the same ammo, so I'm happy with a compromise. I adjust from there...
     
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  7. oO_Rogue_Oo

    oO_Rogue_Oo Well-Known Member

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    Oehler 35P?
     
  8. Nod

    Nod Well-Known Member

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    Mouser, do a google search on "Ballistics by the inch" and you will get some charts that will give you an idea about what your asking.
     
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  9. Mouser

    Mouser Well-Known Member

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    Thanks for the link...that is what I'm looking for. As I will be loading some lead pistol rounds in 45LC and maybe 44mag I wanted to understand where velocities in rifles might approach 1500 fps and the data gives me a good feel for velocity jump...a little more than I thought in 45lc and alot more in 44mag based on their tested load recipes
     
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  10. RJF22553

    RJF22553 Well-Known Member

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  11. SGWGunsmith

    SGWGunsmith Well-Known Member Supporter

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    A couple years ago I ran both of my Ruger Mark II 10-inch barreled pistols through some ballistics recording. One is blued steel, the other is stainless:

    [​IMG]
     
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  12. JimRau

    JimRau Well-Known Member Supporter

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    When you are discussing straight wall cases (1 to 1 expansion ratio which utilize fast burning powders, aka pistol powder) and small powder charges (pistol rounds) you will find that anything past about 14 to 16 in bbl length is a waste.