**HELP** Need to understand trajectory(heavy VS light) in bullets.

Discussion in 'Long Range Hunting & Shooting' started by Popapi, Dec 12, 2010.

  1. Popapi

    Popapi Well-Known Member

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    Here's my question Guys in same bullets(accubond/accubond, VLD/VLD etc.) with one at 130grn and the other at 140-150 which bullet would shoot the flatest at longer ranges(300-700yrds etc)? I've always thought the heavier bullet would have the better trajectory at longer distance being the lighter would run out of steam. EXAMPLE as I look at same bullet trajectories here at federals website the heavier bullet is the one that drops the most. I thought different at LONGER range.

    Federal Premium - Rifle Ballistics

    Explain to me why do we use the heavier bullets as opposed to the lighter for long range. In ending I do understand wind drift in the lighter VS heavier, but trying to understand what's stated up top thanks!
     

  2. Buano

    Buano Well-Known Member

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    The devil is almost always in the details.

    Generally speaking:
    Extremely light bullets start out very fast, then lose energy & speed, after which point they are a slow light bullet. Heavier bullets start out slower but with much more energy due to the added mass, which keeps the bullet from slowing down as fast as a very light bullet would (assuming similar shape). Also, the heavier bullet is apt to be more aerodynamic, which further helps the heavier bullet maintain energy & speed.

    At EXTREME ranges you will see (in most cases) a point where the very light bullet will suddenly drop fast because of the lost speed & you will see where the heavy bullet suddenly is above the light on drop charts. If you never get to these ranges, you will not see this effect!

    For hunting applications, residual energy, the energy at point of impact, is critical to determining how much damage a bullet is apt to do to an animal. For this reason many long range hunters prefer a heavier bullet for long-range big game hunting. For short to medium ranges a lighter bullet is often the better choice because of the flatter trajectory and reduced recoil, which leads to more accurate hits as ranging is less critical.

    Remember, the devil is in the details. Look at the drop charts & residual energy for the loads you are considering & determine which is most advantageous WHERE YOU WILL BE SHOOTING. There is no universally "perfect" loading. If there were only one cartridge & loading would be in universal use.
     

  3. rscott5028

    rscott5028 Well-Known Member

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    I'm no physics expert, but I think weight has something to do with mass in motion, yada yada Perhaps someone can explain the physics of all that... and, mass x velocity = energy which combined with expansion characteristics and bullet placement relate to terminal ballistics and lethality. ...and, then you get vastly different approaches such as the Berger vs Barnes debate.

    None of which really has to do with flat shooting. Trajectory is mostly a function of muzzle velocity and BC.

    In any case you have to keep in mind that for a given diameter bullet to be heavier, it either has to be (a) longer, (b) different shape ogive/tail, and/or (c) different materials.

    Since you indicated "same bullets", I assume you really mean same materials/density. So, the shape/length changed affecting the BC with heavier (meaning longer) bullets often being of a higher BC although, you sometimes get longer/heavy/round nose bullets which are lower BC.

    Also, you want to keep in mind that boat tails, etc have varying effectiveness at different velocities i.e. sub/super-sonic. Hence, some would say that an accurate trajectory curve would be characterized by multiple BCs.

    We usually think of boat tails for long range and associate high velocity with boat tail/VLD. But, I think I read somewhere that boat tails aren't really helping above around 2000fps (or somewhere thereabouts). Hence, flat base bullets are preferred by benchrest shooters out to 200 yds. And, boat tails/VLD shine at longer ranges after their velocity has dropped somewhat.

    I guess that's where the expression came from where people talk about VLDs "going to sleep" after about 200 yds.

    ...just my thoughts. I'd be keen to here from the experts.

    thanks!
    Richard
     
  4. barthmonster

    barthmonster Well-Known Member

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    I read about a guy shoot a long-ish (1900 yards !) shot with a 300 Ultramag using 210-grain VLD's... I wonder with a 150-grain, even a good-one if it would even remain supersonic at that range.
     
  5. rscott5028

    rscott5028 Well-Known Member

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    Also, I beleive most of the external ballistics programs ask for the name/type/weight of the bullet. But, other than the environmental conditions the trajectory curve comes down to velocity and BC.

    ..where BC comes down to the shape of the bullet.

    Also, Newton figured out that 2 objects of radically different weight fall at the same 9.80 meters per second squared.

    Regardless of how far or fast two bullets travel, if they are fired at the same time with the muzzles parallel to the ground, the bulltes will hit the ground at the same time.

    Therefore, weight doesn't do anything for/to trajectory except as to change the shape of the projectile and the shape has everything to do with BC and trajectory.

    Again, that's just my understanding as layman.

    thanks
    Richard
     
  6. rscott5028

    rscott5028 Well-Known Member

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    Well, you probably won't have anyone designing a lightweight bullet for extreme distance shooting because you get into other factors such as the internal ballistics associated with buring powder and launching the bullet and the retained energy at impact. etc...

    But, I suppose it could be done on paper.
     
  7. freebird63

    freebird63 Well-Known Member

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    Now about that idea of a bullet going to sleep, I am still on the fence about that one. But if you have the book called "precision shooting at 1000 yards", on page 224 he mentions the idea of a bullet going to sleep and says its hogwash and it always makes him laugh when someone mentions that. Also somewhere I saw, it might have been on the military channel, a sniper talking about how the bullet spin pulls a bullet back down towards earth. So there we involve the rate of twist in the barrel. So say if a barrel has a clockwise twist and that clockwise spin is truely causing the bullet to come back down or loss elevation, then why have barrel manufactures not experimented with a counter clockwise barrel twist??? I am no expert here but on my tv show I play one "ha ha ha"" but to me in some twisted sort of way it kinda makes sense. I hope someone with more experience will chime in here. Now I am going to have a headache just thinking about it.
     
  8. rscott5028

    rscott5028 Well-Known Member

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    freebird63,

    Thanks for clarifying.

    I have the book you mentioned. It's an excellent resource and I agree with you and the author.

    I was just pointing out that boat tails and VLD bullets don't have the advantage at close range/high velocity over flat base bullets. So, that may be the origin for the notion of "going to sleep". Some people use that as an excuse for poor accuracy at short range thinking that their accuracy will improve over distance. I shure don't subscribe to that theory.

    Nonetheless, it's my understanding that flat base designs dominate 100-200yd benchrest as compared to boat tail/VLD designs which dominate 600+yd competition.

    My thinking is that bullet shape has more to do with trajectory than weight (heavy vs light). Weight has everything to do with energy. And, expansion is what destroys tissue and transfers energy.

    thanks,
    richard
     
  9. LRSickle

    LRSickle Well-Known Member

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    YouTube - Pitching and Yawing of a bullet
    Here's a video that explains the pitching and yawing of a bullet in flight. It is fairly common to shoot, say, a 1.5moa group at 100 yards and a 1moa group at 300. I've seen this happen all the time. I'm pretty sure it's because boatails do indeed go to sleep.

    Actually, with a right-hand twist, the bullet climbs up if the wind is coming from the right and spins down if the wind is coming from the left. It's called spindrift. The riflings score little groves in the bullet that act like fins. If the wind is coming from the right the high pressure is on the right side of the bullet. The bullet is spinning clockwise and grips(?) the wind better on the right side. It's just the opposite for a left to right wind.
    I hope I explained that well enough. I can picture it in my head but I don't know if I can explain it very well.
     
    Last edited: Dec 12, 2010
  10. rscott5028

    rscott5028 Well-Known Member

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    Great video. Everyone that's interested might want to read up on the subject.

    It appears the video came from...
    Homepage of Bryan Litz - A Bravenet.com Hosted Site

    According to Bryan Litz, the author of the computer simulation in the video, "I tried many different things like this, simulated hundreds of 5, 10, and 20 shot groups. Nothing produced smaller angular groups at longer range. [...] Just to be clear about the conclusions of the modeling: The phenomemon of smaller angular groups at longer ranges was not disproven. The only thing I've shown is that if the phenomenon actually happens, epicyclic swerve is not the cause of it."

    So, while he didn't disprove it. I'd be keen to read more about what really happens. I do know that some people beleive in it strongly. So, there must be a reason why they beleive it and why it occurs.

    A less scientific phenomenon that I've observed is, "aim small, miss small." My 14yo son is impatient and doesn't concentrate at short range where he knows it's a kill shot every time. But, he's really focused at longer ranges. I can show you targets where he's shot 1" groups at 100yds and 3" groups at 580 yds. I don't have enough samples to make a statistical inference and shooter concentration that I've attributed this to isn't the same as the bullet going to sleep. But, the point being that there are many variables that result in the POI whether it be short or long range.

    As to the rise/fall due to spin and wind direction, I have seen that written about in some fairly authoritative places.

    thanks,
    richard
     
  11. Buffalobob

    Buffalobob Writers Guild

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    OK, you asked a certain question and what follows is the correct answer.

    The ballistic coefficient is the number which determines the trajectory and it is is composed of two terms. First term is a shape or form factor and the second term is sectional density or weight.

    I would invite you attention to a most useful reference

    exterior ballistics

    The Sierra Exterior Ballistic document is very worthwhile reading. And after a few years of shooting long range you should read it again as some of the small details will be fresh and new and you will learn a lot more once again. The guys who wrote it did a good job.



    I would just add two notes----
    1. High sectional density is not only good for the BC but is good for penetrating animals.
    2. A copper bullet with the same shape factor as a gilded lead bullet will have a low SD and low BC. Conversely a heavy bullet with a round nose will have a high SD but poor shape factor and therefore a low BC. There is a time and place for each type of bullet. The buffalo I killed was with a round nosed bullet at 50 yards from the same rifle I used to shoot high BC bullets 1000 yards.
     
  12. rscott5028

    rscott5028 Well-Known Member

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    excellent resource
    thanks!!!
     
  13. Popapi

    Popapi Well-Known Member

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    Awesome!!!!!!!!!!!!
     
  14. freebird63

    freebird63 Well-Known Member

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    My point was or is, if the riflings are clockwise or counter clockwise, if the riflings are clockwise and the closkwise spin causes the bullet to fall to the earth faster then say a barrel with riflings that were counter clockwise??? have there ever been any experiments with that???? because in my little simple twisted mind it almost makes sense that if a barrel that had clockwise riflings and with the clockwise spin of the bullet it would cause the bullet to fall back to the earth faster then a barrel with a counter clockwise riflings causing the bullet to spin counter clockwise?? also we would have to factor in the rotation of the earth. Welcome to my world, these are just questions I have.
    Chuck