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Gravity

Posted: 01 Aug 2019 07:29
by owejia
Was trimming tree branches from trees that interfered with my line of sight at my shooting range a couple of days ago. When shooting from my shack the trajectory is down hill, guessing about 15 or 20 degrees, does gravity pull the same on the boolit as if shooting level or uphill? Or is gravity always the same ? :?:

Re: Gravity

Posted: 01 Aug 2019 09:57
by orerancher
owejia wrote:Was trimming tree branches from trees that interfered with my line of sight at my shooting range a couple of days ago. When shooting from my shack the trajectory is down hill, guessing about 15 or 20 degrees, does gravity pull the same on the boolit as if shooting level or uphill? Or is gravity always the same ? :?:
Gravity is always the same...
But the amount of Angle does effect Trajectory....

Re: Gravity

Posted: 01 Aug 2019 13:57
by Ohio3Wheels
Here's a link to an article from Rifle Shooter that may shed some light on it.

https://www.rifleshootermag.com/editori ... shot/83768

Make smoke,

Re: Gravity

Posted: 01 Aug 2019 16:41
by mr surveyor
yep, it's mostly "horizontal" and NOT "spatial" distance that needs to be considered.

jd

Re: Gravity

Posted: 04 Aug 2019 06:40
by owejia
Ok if the bullet is being propelled, at the same initial velocity, perpendicular up away from or down toward the center of gravity will the velocity of the bullet be the same in both directions?

Re: Gravity

Posted: 04 Aug 2019 09:28
by RBHarter
Yes ........ sort of .

The duration of effect is the key .

The physics are muddy for me but the mechanics make sense ...........

When shooting down hill the trajectory appears flatter because the bullet is traveling in the same direction as the effect vs up hill where it is going the opposite direction of the effect . In the actual form the up,down, or level flight all have the same reaction to the effect . It appears to be a greater effect mechanically because we "know" that stuff goes down hill faster than up hill .

A 1 second flight time drops 32 ft below the barrel release plane give or take for physics stuff like spin drift and vertical air flow and corialus effect . This holds true whether the bullet exits at 40 or 4000 fps . This is why a 4200 fps 220 Swift appears to shoot so much flatter than a 3100 fps 223 . That 1000 fps at the muzzle changes the flight time to a particular distance and in doing so changes the duration of effect .

To add another log to the fire .... Ballistic coefficients add to the confusion because they also look faster and flatter shooting but in reality they are actually slowing down slower . A .400 BC bullet from a 25, 30,35 and 45 caliber at the same muzzle velocity will have identical flights unfortunately a .400 BC 25 or 30 cal bullet can be sent down range a lot faster than most 35 or 45 cal bullets and because of the weights involved inertia becomes involved in all of this as well and now we're back into the physics ........

Re: Gravity

Posted: 05 Aug 2019 09:16
by Macd
At 15 degrees your true ballistics range (TBR ) is .96% (cosign of the angle) the measured distance from the muzzle to the target. At 20 degrees it is .94 %.. In effect the measured distance is the hypotenuse of a triangle and the TBR the base, the 15 or 20 degrees the slope. Most people overestimate slope. At 100 meters the rise on a 15 degree angle is approximately 27 meters or a pitch of 3.2 in 12. The difference this has on POI is dependent on the ballistics of the round you are firing. A relatively fast bullet with a high BC will have a POI change that is negligible while a slow, low BC one may deviate by a few 10ths of an inch. Higher angles and distances can make the deviations enough to perhaps suggest a compensating hold under or sight adjustment. For example the difference a 30 degree slope makes for on 180 brain 30-06 load is approximately 2.6 inches high at 200 yards and 3.4 inches at 300.

There are smart phone angle finders for anyone who wants to determine a slope or to practice estimating but it all gets too complicated for my old head. No mountain goats here and a moose has a pretty large vital area.

Re: Gravity

Posted: 13 Aug 2019 23:29
by Old Scribe
WHEW!

Re: Gravity

Posted: 03 Sep 2019 02:47
by Fyodor
There is a German saying among hunters to think about point of impact when not shooting level:

Ob rauf, ob runter,
halt immer drunter.

It means, no matter if you shoot uphill or downhill, you need to aim below the point of impact.

Re: Gravity

Posted: 03 Sep 2019 10:48
by larryw
Old Scribe wrote:WHEW!
+1 +corn