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Posted: 11/19/2005 1:38:13 PM EDT
[#1]
gravity wins
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Posted: 11/19/2005 1:39:02 PM EDT
[#2]
every time.
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Posted: 11/19/2005 1:43:15 PM EDT
[#3]
It actually does, during transitional ballistics 2 things occur 1) the projectile speeds up for the brief nanosecond it is free of the friction of the bore and it rises. However, the amount of increase in velocity and rise is very, very small and only lasts a very short distance.
I know when we taught transitional ballistics to student artillery officers, we emphasised that transitional ballistics a relatively unknown subject. |
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Posted: 11/19/2005 1:48:49 PM EDT
[#4]
Your friend is thinking of line of sight not ceterline of bore. LOS deals with trajectory of a sighted in weapon.
However STLRN may have something there. |
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Posted: 11/19/2005 1:57:25 PM EDT
[#5]
If you are holding the barrel perfectly level, then the bullet begins to fall immediately. But if you are aiming straight out the sites, then the bullet will go up a bit before beginning to fall. This is only because the barrel is aimed upwards.
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Posted: 11/19/2005 1:57:48 PM EDT
[#6]
Thats what I was trying to tell them. If your talking line of sight then yes it rises past the first intersection then drops to POI (hopefully). They were saying that the rifling marks make it climb. I said then why up and not sideways? Physics is physics.
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Posted: 11/19/2005 2:18:19 PM EDT
[#7]
your bullet will only climb if your weapon of choice is a golf-ball launcher. then the little dimples of the ball will catch air (as long as the ball has backspin) and it will rise...
So, yes, your friend is right. 
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Posted: 11/19/2005 2:31:35 PM EDT
[#8]
You mean they were wrong. There is no backspin only rotational forces acting equally on all sides at the same time. ( baring any wind pushing on it)
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Posted: 11/19/2005 2:47:30 PM EDT
[#9]
Relative to the centerline of the bore, the bullet follows an arc away from the centerline and downward with the pull of gravity. If the centerline of the bore is parallel with the ground, the bullet will hit the ground at exactly the same time as a bullet dropped by hand.
Now, a properly sighted in gun will fire a bullet through the line of sight twice, first as it goes up through it and then down through it. Here's a theoretical chart of the path of the bullet relative to the line of signt (the line you look through your scope or sights through) Muzzle: -1.5" 10 yards: -1.0" 20 yards: -0.5" 27 yards: dead on 50 yards: +1.0" 100 yards: +2.5" 200 yards: +.5" 250 yards: dead on again 300 yards: -3.0" If you understand your gun and load enough, you can sight your gun in for the first point and it will be close to zeroed at the second point. The Army sights their M16's in at 27 meters I think... something like that. |
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Posted: 11/19/2005 2:49:10 PM EDT
[#10]
Just point your muzzle up. Then you know it will rise.
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Posted: 11/19/2005 2:51:13 PM EDT
[#11]
Thats exactly what I'm saying.
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Posted: 11/19/2005 3:02:31 PM EDT
[#12]
define rise
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Posted: 11/19/2005 3:04:33 PM EDT
[#13]
I get a rise shooting guns...
oh wait, wrong thread... 
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Posted: 11/19/2005 3:09:31 PM EDT
[#14]
Rise as in rise above a line drawn through the barrel to the POI.
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Posted: 11/19/2005 3:11:14 PM EDT
[#15]
A bullet does not rise above the boreline. Never.
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Posted: 11/19/2005 3:11:58 PM EDT
[#16]
that would be the bore line so no.
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Posted: 11/19/2005 3:12:11 PM EDT
[#17]
The blast of escaping gasses as the bullet leaves the muzzle could account for an increase in velocity, but I'm at a loss to come up with anything consistent with the laws of physics as they are currently understood that would make the bullet suddenly jump up. Do you have any source with emperical data or even any plausible explanation for that part? |
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Posted: 11/19/2005 3:13:15 PM EDT
[#18]
I like how you think, short and to the point.
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Posted: 11/19/2005 3:13:33 PM EDT
[#19]
The presssure would escape equally around the bullet base as it left the barrel. It's BS. |
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Posted: 11/19/2005 3:18:24 PM EDT
[#20]
The bullet would have to have a shape like an airplane wing to create a negative pressure above it to cause a rise, being that it rotates totally negates the premise. Correct?
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Posted: 11/19/2005 4:04:48 PM EDT
[#21]
Just some thing I learned in the Gunnery Instructor rehearsal program. It goes along with tube jump, in which the tube actually whipped upward as the round goes down it. Often flinging the round slightly up as it leaves the tube.
Also, rifled projectiles actually porpoises and oscillate both above and below the axis of flight for some distance after leaving the tube. Even for the 5.56mm it takes 27 meters for the round to stabilize. |
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Posted: 11/19/2005 4:16:50 PM EDT
[#22]
Interesting...
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Posted: 11/19/2005 5:00:02 PM EDT
[#23]
the law of gravity can not be broken, an object that does not generate its own lift start to fall immediately -- that said, an earlier post is correct that the round may appear to rise above the axis (or wonder off to any of many points beside or below) as the barrel is stressed and whips when the gun is fired. Watching highspeed video of this is amazing really, the amount of flex is impressive. The whip effect at the tip of the barrel actually tends to be more of a circle if you will.... point your finger straight out and make little circles with it. The bullet continues this pattern in flight and appears to rise and fall above and below the bore axis -- as a rule, it can take as much as 70 yards for a rifle round to stabilize in its path.
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Posted: 11/19/2005 5:01:42 PM EDT
[#24]
Fire a bullet and drop an identical one from muzzle height simultaneously and they will both hit the ground at the same time. Gravity, 23ft/sec/sec
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Posted: 11/19/2005 5:10:00 PM EDT
[#25]
have a tshirt "Gravity: It's not just a good idea, it's the LAW!" |
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Posted: 11/19/2005 6:29:05 PM EDT
[#26]
If I remember my physics correctly, the acceleration (downward) due to gravity is 32 ft/sec/sec. The other part - dropping a bullet or firing it horizontally making no difference is correct, Except for the time effects of air resistance. (Even Galileo didn't have it exactly right - a lead ball dropped from the Tower of Pisa simultaneously with a styrofoam ball [before Gali's time] would hit the ground before the styrofoam ball, UNLESS both are dropped in a vacuum).
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Posted: 11/19/2005 10:00:01 PM EDT
[#27]
Way off topic, but did you know that when the Navy used to shoot those big 16 inch guns, the projectile flight time was so long that the rotation of the earth had to be calculated in order to get the round on target?
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Posted: 11/19/2005 11:22:50 PM EDT
[#28]
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Posted: 11/20/2005 1:45:51 AM EDT
[#29]
true only in a vacuum, in atmosphere there is a slight amount of lift provided by the air. |
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Posted: 11/20/2005 2:06:56 AM EDT
[#30]
Really? Interesting. So if one were to fire 10 rounds of 5.56 all at the same time from 10 different rifles, and each of the rounds had a different powder charge, they would all still hit the ground at the same time but just at different distances? Thanks. |
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Posted: 11/20/2005 4:38:06 AM EDT
[#31]
If I understand this correctly, there is instability in the bullet's fllight for the first few yards. During the period of time it takes for the bullet to stabilize, it is not dropping, and may actually rise. Therefore, the bullet which is dropped will strike the ground a few milliseconds before the bullet fired from the barrel aimed at a perfect right angle to the earth.
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Posted: 11/20/2005 5:47:56 AM EDT
[#32]
Gravity wins, of course, but if a bullet rises at all, it would be do to aerodynamic lift. Every object moving through air has a lift coefficient...it may be that at certain speeds and spin rates a rifle round has slight positive lift, which would cause it to rise. As it slows down and the lift coefficient drops to less than can support the weight of the bullet, the inevitable sink begins.
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Posted: 11/20/2005 6:36:02 AM EDT
[#33]
But why only lift? (up direction) Why not left or right? I think the only force acting on the bullet minus wind is gravity. I don't see how it can generate lift. Unless the rifling marks do somehow.
I understand what Gunzilla and Geohans are saying about a bullet direction before it stabilizes, but I don't think that constitutes lift. I like to think of that as more of a corkscrew action as it travels through the boreline. |
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Posted: 11/20/2005 6:38:44 AM EDT
[#34]
STLRN, you are talking about BARREL WHIP, not projectile drop from the muzzle. This was well known in the early part of the twentieth century, at the time the British adopted the SMLE infantry rifle. Because of receiver and bolt flex, the muzzle of the barrel would flex UPWARD as a bullet of lower velocity exited the muzzle, while the muzzle would not flex upward nearly as much with a higher velocity round. As a result, for long distance shooting, the vertical dispersion of the group would be much smaller than groups fired with the same ammunition in a Mauser type actioned rifle. This phenomenon was known as "compensation". The Brits much favored the SMLE rifle for long distance shooting for many years. They used Mauser actioned rifles for shorter ranges, but stuck with the SMLE action for longer ranges, up until the end of the 303 days. Target shooting in the British Empire was done strictly with government issued ammunition in those days and some of it was not so uniform, velocity wise. So, while the muzzle of your artillery piece would be at a higher elevation at the instant of exit, the projectile would still start to drop at the instant of exit.
Cheers, Phil |
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Posted: 11/20/2005 8:26:39 AM EDT
[#35]
Phil
In artillery terms we call it "Tube Jump." It is probably the same thing you are refering to. |
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Posted: 11/20/2005 8:41:11 AM EDT
[#36]
Coriolis Effect |
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