drop of a bullet vertically vs. horizontally - Page 2


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Old 01-18-2008, 11:49 AM   #11
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No, you don't need a vacuum. The air will act equally on both objects if both objects are equal in mass and weight, which they are since "they" are both identical bullets.
You would only need a vacuum if the two dropped items are of equal weight, but of differing mass. A 55 grain balloon would fall as fast as a 55 grain bullet in a vacuum, but we didn't start out talking about balloons, bullets, and vacuums, only bullets.
Equal mass, equal weight, equal fall rate regardless of lateral velocity. Unless there is a force to counter act gravity, everything falls.
Gravity always wins, it may take a million years, but gravity wins.



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Old 01-18-2008, 01:17 PM   #12
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No Duck. The OP said the barrel is level. Bullets do not rise if the barrel is parallel to the ground. They actually start dropping as soon as they leave the barrel. If the bullets are the same weight they will hit the ground at the same time. It's physics. You are comparing paper and a rock totally different from two identicle objects.



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Old 01-18-2008, 01:48 PM   #13
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It is a very common misconception that bullets rise as they leave the barrel because of the advertising showing an arc trajectory. There is only an arc because the barrel is pointed upward in relation to the sighting device. The sights/scope must be misaligned to compensate for the drop. The bullet drops "relative to the bore", disregard the point of aim.
Gravity is a constant 32.2 feet per second per second (F/S/S). If you shoot a bullet from a level bore at 32.2 feet above the level ground the bullet will be in the air for EXACTLY 1 second. Velocity does not matter. Weight/mass does not matter. Ballistic coefficient does not matter. A .45 ACP 230 gr FMJ at 830 fps will hit the ground at the same time as a 55 gr FMJ fired at 3200 FPS out of a 5.56 mm. The 5.56 mm will travel FARTHER in that one second but will be in the air for the EXACT same amount of time.

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Old 01-18-2008, 05:43 PM   #14
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Is that right? Interesting. I would think the heavier bullet would hit the ground first. The foward velocity does not matter but if both were held next to each other and dropped at the same time I'd think the .45 would hit the ground sooner.

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Old 01-18-2008, 05:52 PM   #15
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Originally Posted by robocop10mm View Post
It is a very common misconception that bullets rise as they leave the barrel because of the advertising showing an arc trajectory. There is only an arc because the barrel is pointed upward in relation to the sighting device. The sights/scope must be misaligned to compensate for the drop. The bullet drops "relative to the bore", disregard the point of aim.
Gravity is a constant 32.2 feet per second per second (F/S/S). If you shoot a bullet from a level bore at 32.2 feet above the level ground the bullet will be in the air for EXACTLY 1 second. Velocity does not matter. Weight/mass does not matter. Ballistic coefficient does not matter. A .45 ACP 230 gr FMJ at 830 fps will hit the ground at the same time as a 55 gr FMJ fired at 3200 FPS out of a 5.56 mm. The 5.56 mm will travel FARTHER in that one second but will be in the air for the EXACT same amount of time.
That logic doesn't work either. If I shoot a bullet out of a perfectly level barrel at 32.2 feet in the air it will travel in the air far longer then 1 second. Think of some of the 50 caliber rifles. Those rounds can travel miles before hitting the ground. The rifling of a bullet spins the bullet so fast leaving the barrel it will keep it going level longer. Now a 12 gauge slug might hit the ground in a second, but a high powered rifle will travel longer in the air.
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Old 01-18-2008, 06:02 PM   #16
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Ok I got to thinking about this more. So if this were true, I shoot a gun with a velocity of say 2500 FPS. I shoot it from a height of exactly 32.2 feet in the air and perfectly level. With no outside factors like rain or wind acting on it, it will strike the ground 2500 feet out and and exactly 1 second later? HMM...This could make sence but I would have to see it to believe it. I still think the rifling may effect the outcome of this test.

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Old 01-18-2008, 09:25 PM   #17
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The rifling gives the bullet stability, not lift. The bullet fired at 2500 fps will not strike the ground 2500 feet away 1 second later. Air friction acts upon the bullet immediatley upon leaving the barrel so it begins to slow down. depending on the ballistic coefficient (how much the air friction effects it) it will hit the ground some where less than 2500 feet away.
This whole concept runs counter to what the "traditional wisdom" has taught us. It can be a hard pill to swallow but true.
Physics class in High School was never this interesting or thought provoking, was it? I had the good fortune of taking Physics for Criminal Justice Majors in college (2 semesters) and the professor used real world examples like this to spur learning. Then later I attended 160 hrs of Accident Investigation and Reconstruction. We used problems like this to understand the physics involved in motor vehicle crashes. Science is cool. Wish I had teachers in High School that understood how to make a topic fun.

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Old 01-19-2008, 01:52 AM   #18
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Correct except line of bore is BELOW line of sight. Think about it: sights or scope on a gun (line of sight). Above or below the barrel?
Here's an experiment for you. Take a bolt action rifle (You will see why I said a bolt action in a moment) , sight it in for, say, 300 yds. Sandbag it so it will not move, align the sights on the target 300 yds away. Then carefully, without disturbing the sight alignment, remove the bolt. When you squat down and peer thru the bore, you will find it pointed somewhat above the target. There are always two points that are exactly on where the sights point, One is when the bullet is on the way up, (this is because, as you said, the sights are above the bore) and the other is when the bullet is on the way down. I seem to remember that a 30/06 sighted in at 150 yds is also on at 50 yds. This phenomenon is called mid-range trajectory and is listed in most performance charts. It is the highest point a bullet attains on the way to the point of aim. Point blank means that the target is so close that mid-range trajectory doesn't come into the calculation. The time in flight is so small that the bullet doesn't have time to fall any appreciable amount.
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Old 01-19-2008, 02:23 AM   #19
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Yes the barrel might be pointed above the scope or sights but physically the line of sight is above the bore.

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Old 01-19-2008, 02:32 AM   #20
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Yes the barrel might be pointed above the scope or sights but physically the line of sight is above the bore.
Think outside the box. The term used was "line of bore" not just plain "bore".
If you want to talk about the hole in the end of the barrel, yes, the sights are above that. However the "line of bore" is the projected line down the center of the bore from the breech to the muzzle and beyond, all the way out into the distance. The same thing with "line of sight". It's not just where the sights are on the barrel, it's all the way to the target when the sights are aligned on the target.


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