Velocity Magnatude Questions

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by eddybo, Apr 21, 2010.

  1. eddybo

    eddybo Well-Known Member

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    Okay I have had someone else trying to explain this to me but it has not soaked into my thick skull. Maybe someone here can explain where I can understand.

    Maybe I am retarded but it makes no sense to me that taking two identical bullets leaving a bore at differing velocities that the slower bullet would ever travel further that the bullet that had the higher velocity.

    Here is the part of the explanation that I have been given that I do understand. A bullet leaving the muzzle at a faster velocity has greater forces applied upon it. Like the difference between sticking your arm out the window at 40 and at 80 miles per hour.

    Here is my problem with the whole explanation. My inability to grasp this apparently counter intuitive concept comes at this point. Once the faster bullet slows to the same velocity as the slower bullet would the forces being applied upon the bullets be the same and at that point both slow at the same rate?
     
  2. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Eddybo,

    no, you've got it just right here. If we're talking about two identical bullets being fired at the optimum angle for max distance, the one that starts off faster will go farther.

    Is it possible that there was something that was missed in relating this, such as a more streamlined, heavier, higher BC bullet being fired at a lower velocity? Plenty of examples there, and that makes perfect sense. Otherwise, I'm missing something here. Are we talking theoretical flight in a vacuum?

    Kevin Thomas
    Lapua USA
     

  3. elkaholic

    elkaholic Well-Known Member

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    +1......No rocket science there if the bullets re indeed identical......Rich
     
  4. LouBoyd

    LouBoyd Well-Known Member

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    The way the faster bullet could travel a shorter distance is if it deforms or breaks up.
    That can happen with fast twist barrels and light weight bullets. Bullets which are identical before firing certainly don't have to remain identical over their trajectories.
     
  5. Buffalobob

    Buffalobob Writers Guild

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    Well, that settles it for sure.

    Being as you now know that 338 AM don't give you any advantage over the 33 Win in a 1886 lever gun I am guessing you are really down in the dumps. Just to cheer you up I'll swing by Walmart and get you a nice 338 Federal in nice plastic mattie mattel armalite and you can hand off that powder guzzling AM to me.
     
  6. elkaholic

    elkaholic Well-Known Member

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    I would certainly agree with that! I was coming from premise that the bullet was starting and staying the same. Who ever made the original comment to the poster would have to be quized a little I guess:D
     
  7. eddybo

    eddybo Well-Known Member

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    Yall seem to believe similar to my own thoughts on the subject. This started over on the hide. I had a post regard the 375/416 that I am going to be playing with. I was told that I would be launching the bullets too fast and that they would slow down to fast. I thought they were just jacking with me, but did not want call them on it. I finally got curious and sent a PM to one of the guys. He tried to explain it but I am not seeing it. Now I know one of these guys "Later" while we have never met have several mutual friends and have conversed on the phone several times.......is he jacking with me? Later knows a lot of crap I am sure he knows more minutia about external ballistics than I do. The only thing I know about this stuff is functional.

    416 barret brass quality??+ other ????s - Sniper's Hide Forums
     
  8. Buffalobob

    Buffalobob Writers Guild

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    The slower bullet will, as time goes by, get closer in speed to the faster bullet but it approaches it asymptotically and never ever becomes equal in speed with the faster bullet.

    All you have to do is to run the same bullet such as the 300 SMK at 3200 fps and at 3300 fps and see what the speeds are at 1000, 2000, and 3000 yards.
     
  9. MontanaRifleman

    MontanaRifleman Well-Known Member

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    After reading that thread, "Later" is either jacking you around or doesn't have a clue what he is talking about. There are only two things that matte in external ballistics in short, medium, long or any range, and they are velocity and BC, period. It's very easy to demonstrate by playing with a ballistic calc. If you have two identical bullets leave the muzzle at different velocities, the faster one is going to get to the same point (any point) faster and go farther, and buck wind better. If you have two bullets leaving the muzzle at the same velocity, the one with the higher BC will get down range faster, blah, blah , blah, period. don't matter what caliber weight or anything else. BC and velocity are the only things that count. Just run a couple of ballistic calcs and ask "Later", uhhhh.... what abou this??? :)
     
  10. eddybo

    eddybo Well-Known Member

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    I dunno, yalls thoughts are the same as mine. I was just wondering if there was something I was missing, some obscure theory or something. I have run a 375 gr bullet with a BC of .94 though exbal using both velocities, faster always wins.
     
  11. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Eddybo,

    after taking a peek at the link you posted to Later's comments, it seems to me that things were just taken a bit out of context. I didn't get that he was saying anything about identical bullets, or that the slower bullet would go further because of air drag, etc.. He's correct about the faster bullet suffering more resistance. This resistance is roughly proportionate to the square of the velocity, sort of like how kinetic energy is calculated. Double the velocity and you've roughly quadrupled the atmospheric resistance. However, once you compare two identical bullets that have arrived at the same velocity, the trajectory, energy, drag, etc., is going to be identical.

    Here's a simple illustration; Maximum range is acheived at a departure angle of 45 degrees in a vacuum. No atmospheric resistance involved in that case, so the departure angle is the same for the max range of any projectile. In the real world, that departure angle needs to be about 30-33 degrees for a typical centerfire rifle, due to the atmospheric resistance, i.e., drag. However, a typical mortar usually hits its maximum range when the departure angle is close to 45 degrees, just like the theoretical vacuum trajectory. The difference here is velocity. The mortars are typically fairly low velocity, and as a result suffer much less drag compared to a higher velocity projo. Any clearer now?

    Hope this helps,

    Kevin Thomas
    Lapua USA
     
    Last edited: Apr 22, 2010
  12. eddybo

    eddybo Well-Known Member

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    Kevin your explanation makes perfect sense, but the context is correct, based on PMs with one of the other posters.

    The premise still is that identical bullets launched at differing speeds, that the faster bullet will somehow travel a lesser distance. I cannot see it, but thought maybe my lack of a science background caused my blindness.
     
  13. elkaholic

    elkaholic Well-Known Member

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    You see VERY clearly:D
     
  14. MontanaRifleman

    MontanaRifleman Well-Known Member

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    Yes you do see cleary. I went back and read the thread again a little more slowly. Those guys really don't understand physics and ballistices very well at all. They dont even mention the term BC and misunderstand the relationships and meanings of velocity, energy, mass, inertia, etc. With many, if not most bullets, BC actually increases (increased resistance to drag) with velocity. For example these GS bullets...

    The GS HV .308 177, .638 @ 3300 fps, .603 @ 2450 fps and .589 @ 1600 fps.

    GS CUSTOM BULLETS - Specifications for use

    The GS SP .338 295, 1.010 @ 2850 fps, .973 @ 2025 fps and .760 @ 1200 fps.

    GS CUSTOM BULLETS - Specifications for use

    You will also see this with the SMK's. The ballistic calculators don't lie. The greater the velocity of a bullet, the faster it will get to point A and point B and point C and so on... and it will go farther, and it will buck wind better, etc., etc.