Gravity

Something been on your mind that you have always wanted to ask and google is no help. Ask it here!
owejia
Posts: 7
Joined: 18 Jul 2019 15:22
My Press Choice: Single Stage
Location: West Tn
Been thanked: 5 times

Gravity

Post 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 ? :?:
orerancher
Supporter
Supporter
Posts: 258
Joined: 15 May 2018 16:37
My Press Choice: Single Stage
Location: Oregon
Has thanked: 94 times
Been thanked: 74 times

Re: Gravity

Post 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....
Ohio3Wheels
Supporter
Supporter
Posts: 888
Joined: 06 Mar 2016 16:09
My Press Choice: Hand Press
Location: SW Ohio
Has thanked: 156 times
Been thanked: 240 times

Re: Gravity

Post 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,
Curt.......makin' smoke and raising my carbon foot print one cartridge at a time +guns +guns
User avatar
mr surveyor
Founding Member
Founding Member
Posts: 649
Joined: 30 Jun 2013 09:30
My Press Choice: Hand Press
Location: NE Texas
Has thanked: 385 times
Been thanked: 231 times

Re: Gravity

Post by mr surveyor »

yep, it's mostly "horizontal" and NOT "spatial" distance that needs to be considered.

jd
--------------------------------------------------------------------------------------
There's just some things best left unsaid on the internetsuperhighway.
owejia
Posts: 7
Joined: 18 Jul 2019 15:22
My Press Choice: Single Stage
Location: West Tn
Been thanked: 5 times

Re: Gravity

Post 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?
User avatar
RBHarter
Founding Member
Founding Member
Posts: 2040
Joined: 13 Mar 2014 19:45
My Press Choice: Single Stage
Location: The green hell 90 miles north of Texarka
Has thanked: 76 times
Been thanked: 670 times

Re: Gravity

Post 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 ........
Just a Red neck,White boy, Blue blood American.....
User avatar
Macd
Supporter
Supporter
Posts: 1009
Joined: 16 Oct 2017 16:12
My Press Choice: Single Stage
Location: Far East
Has thanked: 362 times
Been thanked: 403 times

Re: Gravity

Post 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.
User avatar
Old Scribe
Supporter
Supporter
Posts: 369
Joined: 02 May 2015 09:13
My Press Choice: Turret
Location: State of Jefferson
Has thanked: 461 times
Been thanked: 120 times

Re: Gravity

Post by Old Scribe »

WHEW!
"Well here's another nice mess you've gotten me into." Oliver Hardy
User avatar
Fyodor
Founding Member & Supporter
Founding Member & Supporter
Posts: 1512
Joined: 04 Jan 2014 05:45
My Press Choice: Progressive
Location: Gernsbach, Germany
Has thanked: 794 times
Been thanked: 504 times

Re: Gravity

Post 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.
"I disapprove of what you say, but I will defend to the death your right to say it"
- Evelyn Beatrice Hall, often misattributed to Voltaire

I think I'm thinking, therefore I may possibly be.
larryw
Founding Member & Supporter
Founding Member & Supporter
Posts: 1123
Joined: 20 Dec 2013 11:09
My Press Choice: Single Stage
Location: Arizona
Location: Arizona
Has thanked: 688 times
Been thanked: 327 times

Re: Gravity

Post by larryw »

Old Scribe wrote:WHEW!
+1 +corn
A day late & A dollar short? Story of my life +guns
Post Reply

Return to “Question Of The Month”