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357magnum 7 inch vs 5 inch barrel

tone59tone59 Member Posts: 670 ✭✭
edited April 2015 in Ask the Experts
Since 7 inches is 40% more than 5 inches does it give the round being fired 40% more velocity/energy?
thank you.

Comments

  • bpostbpost Member Posts: 31,171 ✭✭✭✭
    edited November -1
    No the gain is not linear.
  • savage170savage170 Member Posts: 36,545 ✭✭✭
    edited November -1
  • tone59tone59 Member Posts: 670 ✭✭
    edited November -1
    savage170...thank you.
    It looks like 10-15% more energy from a 7in vs 5.
    I am not so sure about the chart numbers though.
    It shows similar ballistic for a 44mag and 357mag from a 4in barrel.
    Having fired both a model 29 44mag. and a model 28 357mag.both being 4 inchers,it is ridiculous that the energy numbers are close.
  • tsr1965tsr1965 Member Posts: 8,682
    edited November -1
    As has been stated, the gain is not linear. It is not linear, for added powder, either, in most cases. Once you hit a rounds, peak efficiency, it takes a lot of doing to gain very little performance wise.

    As far as energy goes, that number is highly skewed, in my opinion, by squaring the velocity, in other words, multiplying by the velocity twice. However, if you proportionalize bullet weights, stuff the 357 with a 180 grain bullet, and the 44 with a 300 grainer, you will see a big difference. There is just no way, that pushing nearly double the mass, at the same velocity, can be remotely close, in this case.

    Best

    EDIT 1
    quote:IE as a deliberately ridiculous example, a good pro bowler will release his 15 lb bowling ball at 21 mph, to yield 220 ft-pts of "muzzle" (or "lane"!) energy. Compare to, say, a 135 grain .38+P fired from a 2" bbl snubnose revolver at 860 fps, which also (by coincidence ) yields the exact same 220 ft-lbs of energy.


    Beantown,

    In all fairness, in green should all be converted to either grains, or pounds, and in red all to mph or fps...[:D][:D][:D]

    EDIT 2

    quote:quote:
    Originally posted by savage170

    Here is a link to barrel length chart http://www.ballisticsbytheinch.com/357mag.html



    Interesting.

    Velocity peeks with a 16" barrel, drops for the 17" and increases slightly with an 18".

    Cannot imagine what could happen to cause this.

    Any ideas?


    With the array of specialty loads, those charts mean nothing. There are specific loads with heavy bullets and fast powders, designed specifically for short barrels, that after 7-8 inches would drop like a rock, and probably get stuck in a 16" barrel.

    Then, in the other direction, one could conceivably pump enough Winchester 780 into a 357 case, and loaded with a 125 grain pill, it could still be gaining velocity in a 20" barrel.
  • beantownshootahbeantownshootah Member Posts: 12,775 ✭✭✭
    edited November -1
    quote:Originally posted by tone59
    Since 7 inches is 40% more than 5 inches does it give the round being fired 40% more velocity/energy?
    thank you.


    No.

    As a moments consideration should (hopefully) reveal, this is virtually NEVER true.

    IE you can't double your velocity by going from a 2" to 4" barrel, or a 3" to 6" or a 4" to 8", let alone quadruple it by going from 2" to 8", or increase it by a power of 10 by going from a 2" snubnose to a 20" rifle!

    It might be true that you get a linearly proportionate increase in velocity given a sufficiently short barrel (eg a 1" bbl .357 very well might give twice the velocity of a 1/2" one), but this is more of a theoretical construct than any situation relevant to "real world" guns.

    A good rule of thumb/ballpark is an extra 75fps muzzle velocity per extra barrel inch, for barrel lengths in the "normal" range. At some point (typically around 18-26", again depending on load, barrel, etc) more barrel length not only doesn't increase velocity, it actually DECREASES it due to increased barrel friction.

    Exact gain will depend on the exact load, type of barrel, and what length you're starting with, but that's more or less what you will see with an extra 2" in a .357 magnum handgun barrel in the range where more barrel still helps. IE, going from a 5 to 7" barrel should give you around another 150fps, and that's what the ballistics numbers show.

    In terms of ENERGY, remember that kinetic energy is proportionate to the SQUARE of velocity. That's why lightweight FAST bullets can have as much energy as heavier slower bullets. This does NOT necessarily mean that light/fast outperforms slow/heavy. . .that depends on many other factors, including (and especially) the bullet construction and nature of the target.

    This is also why kinetic energy alone is a relatively poor measure of so-called "stopping power". If you want to try and create a model, you have to look at other things too, including bullet cross sectional area, mass, momentum (eg "power factor"), etc.


    Edit: I guess what I'm saying is that its not the length of the barrel that counts, its the skill of the shooter. While I guess we'd all prefer to have 7 inches if we could, if you're feeling inadequate, remember that 5" is still well above median length for a American .357 magnum barrel! [;)]

    OK, bad length jokes aside, realistically, I kind of doubt anything on the receiving end of a .357 magnum is going to be able to tell the difference between a bullet fired from a 5" vs a 7" bbl. IMO the small difference in energy is probably only going to matter in an otherwise marginal shot at a handgun distance where you probably shouldn't have taken that shot to begin with. The biggest difference between 5 and 7" bbls is going to be a little less muzzle flip, flash, and blast from the 7" barrel, along with longer sight radius (if you're using iron sights). 7" gun is, obviously, a little harder to carry, and very slightly slower to get into position.

    Edit #2: Some think diameter (caliber) matters more than length. [;)].

    quote:
    In all fairness, in green should all be converted to either grains, or pounds, and in red all to mph or fps.You're right. The point was just to show that by itself kinetic energy isn't all that helpful in establishing wounding potential.

    I deliberately didn't want to clutter the post with all the units and numbers, but since you are asking, here you go:

    KE = 1/2 MV^2 Note that strictly speaking, grains and pounds are units of FORCE, not MASS. (Pounds represent mass x acceleration of gravity). We'll correct for that below.

    21 mph = 31.8 fps

    Bowling ball KE= (1/2)(14#)(31.8fps)^2 = 7078 lb-ft^2/sec^2

    Divide by G (to convert lbs weight into mass) and you get
    (7078 lb-ft^2/sec^2)(32 ft/sec^2) = 221 ft-lbs energy for the bowling ball.

    135 grains = 0.0193 lbs. Same math again, slightly abbreviated. . .

    (1/2)(0.0193#)(860fps)^2 = 7137 lb-ft^2/sec^2
    (7137)/(32) = 223 ft-lbs energy for the .38 special snubnose bullet.

    Note that although I did deliberately select one particular .38 snubnose round to make the numbers here almost exactly the same, both the bowling ball velocity/weight and bullet ballistics are normal/common "real world" examples, you'd see any any range or bowling alley. We're not talking about some exceptionally strong/weak bullet or unusual bowler!
  • beantownshootahbeantownshootah Member Posts: 12,775 ✭✭✭
    edited November -1
    quote:Originally posted by tsr1965
    As far as energy goes, that number is highly skewed, in my opinion, by squaring the velocity, in other words, multiplying by the velocity twice. However, if you proportionalize bullet weights, stuff the 357 with a 180 grain bullet, and the 44 with a 300 grainer, you will see a big difference. There is just no way, that pushing nearly double the mass, at the same velocity, can be remotely close, in this case.

    To be clear, if you push double the mass at the same velocity you double the kinetic energy. That's a pretty straightforward calculation.

    Agreeing 100% with everything you wrote above, the kinetic energy formula isn't really "skewed" in the sense that it does represent an exact measure of a particular physical characteristic. Light bullets going fast, can pack on tremendous amounts of kinetic energy. In some cases, this is "good". . .it explains, for example, part of the empirically disproportionate wounding efficacy of lightweight 55 grain .223 bullets moving at Mach III!

    What's "skewed" is people's perception that a bullets efficacy is directly proportionate to its kinetic energy at the muzzle! Contrary to popular (mis)belief, kinetic energy is *NOT* the same thing as "stopping power", and the two may not even be well related.

    IE as a deliberately ridiculous example, a good pro bowler will release his 15 lb bowling ball at 21 mph, to yield 220 ft-pts of "muzzle" (or "lane"!) energy. Compare to, say, a 135 grain .38+P fired from a 2" bbl snubnose revolver at 860 fps, which also (by coincidence [;)]) yields the exact same 220 ft-lbs of energy.

    If you were standing next to me in a bowling alley, which would you rather have me do. . .shoot you with my .38, or throw the bowling ball at you? [:p] Hey. .they have the SAME kinetic energy!
  • charliemeyer007charliemeyer007 Member Posts: 7,348 ✭✭✭
    edited November -1
    A 357 mag loaded with fast powder for use in a short barrel vs a 44 mag with slow powder for use in a long barrel can narrow the gap. Shoot them at night and compare the flash of un-burnt powder. The N in 44 is lighter because it bigger holes in the steel. Perceived recoil from the lighter gun is higher.
  • Don McManusDon McManus Member Posts: 21,964 ✭✭✭✭
    edited November -1
    quote:Originally posted by savage170
    Here is a link to barrel length chart http://www.ballisticsbytheinch.com/357mag.html


    Interesting.

    Velocity peeks with a 16" barrel, drops for the 17" and increases slightly with an 18".

    Cannot imagine what could happen to cause this.

    Any ideas?
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  • beantownshootahbeantownshootah Member Posts: 12,775 ✭✭✭
    edited November -1
    quote:Originally posted by Don McManus
    Interesting.

    Velocity pe[a]ks with a 16" barrel, drops for the 17" and increases slightly with an 18".

    Cannot imagine what could happen to cause this.

    Any ideas?

    Here's the relevant table, so readers can know what you're talking about. For simplicity I've left off the ammo types, but each column represents a different bullet type/brand.

    18" 1718 2113 1941 1936 2072 1719 2017 1721
    17" 1686 2067 1947 1907 2026 1689 2009 1712
    16" 1790 2119 2004 1946 2051 1739 2044 1741
    15" 1728 2069 1942 1915 2032 1708 2012 1718
    14" 1691 2054 1933 1897 2017 1732 1993 1715
    13" 1682 2024 1916 1885 1979 1674 1984 1687

    I have a very simple explanation for the numbers in blue.

    When the testers chopped down the test barrel from 18" to 17" they accidentally left a slight burr or roughness near the crown. That slightly slowed down the velocity for testing at 17". Further cutting of the barrel removed the burr, correcting the problem for the rest of the table.

    I can think of other similar non-ballistic explanations (eg issue with chronograph during second fire string, environmental temperature difference during testing of second string, etc).

    Also, as a matter of practice, the difference here is pretty minimal. EG for the 158 grain Hydroshock in the last column, I'd say 1715, 1718, 1741, 1712, and 1721 (ie all shots between 13 and 18" bbls) are basically the "same number". A few fps difference is WELL within the normal range of expected statistical variation. A few other bullet types also show very little variation past 13"

    The absolute biggest "gain" here is still under 50 fps from 17 to 18". That's a little bit more, but still probably within an acceptable range for ordinary statistical variation between shots in a box of commercial ammo.
  • AmbroseAmbrose Member Posts: 2,721 ✭✭✭
    edited November -1
    I have Ruger Blackhawk revolvers. Fired with identical loads, results as follows:

    4 5/8" 1167 fps
    6 1/2" 1308 fps
    10 1/2" 1457 fps

    FWIW
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