The Firing Line Forums

Go Back   The Firing Line Forums > The Hide > The Art of the Rifle: Bolt, Lever, and Pump Action

Reply
 
Thread Tools Search this Thread
Old June 30, 2013, 12:47 AM   #1
shredder4286
Senior Member
 
Join Date: May 13, 2010
Location: NE Washington
Posts: 361
Sigting in from an elevated position

Our backyard rifle range is 100 yds, but the bench is about 10' higher than the target.

What I'm wondering is- how much different will my p.o.i be if I were to take a shot at 100 yds without being elevated after being sighted in from the elevated bench? (I.e. hunting)

I'm assuming it would make some difference, just not sure how much.
shredder4286 is offline  
Old June 30, 2013, 01:21 AM   #2
big al hunter
Senior Member
 
Join Date: March 12, 2011
Location: Washington state
Posts: 1,558
I would bet my favorite rifle that you could not see the difference.
__________________
You can't fix stupid....however ignorance can be cured through education!
big al hunter is offline  
Old June 30, 2013, 05:14 AM   #3
Jimro
Senior Member
 
Join Date: October 18, 2006
Posts: 7,097
Cosine angle times range equals true horizontal distance for drop.

By my math that is a 1.9 degree slope.

Cosine 1.9 x 300(feet) = 299.8 feet.

Jimro
__________________
Machine guns are awesome until you have to carry one.
Jimro is offline  
Old June 30, 2013, 08:22 AM   #4
oneoldsap
Senior Member
 
Join Date: September 16, 2009
Location: I live in the foot of the Green Mountains of Vermont
Posts: 1,602
No difference !
__________________
Don't forget to have your liberals spayed or neutered !
oneoldsap is offline  
Old June 30, 2013, 03:39 PM   #5
shredder4286
Senior Member
 
Join Date: May 13, 2010
Location: NE Washington
Posts: 361
Quote:
Cosine angle times range equals true horizontal distance for drop.

By my math that is a 1.9 degree slope.

Cosine 1.9 x 300(feet) = 299.8 feet.

Jimro
So, by math, the difference would be .2 feet of difference in drop. That's what I needed to know- thanks folks!!
shredder4286 is offline  
Old June 30, 2013, 03:48 PM   #6
WWWJD
Senior Member
 
Join Date: February 9, 2011
Location: Central KY
Posts: 552
No; JIMRO's math is saying that your effective range is 299 ft vs. 300 on level ground. Your difference in drop is going to be immeasurable... just in case his answer was misconstrued.
__________________
~Mark

NRA Endowment FTW
WWWJD is offline  
Old July 1, 2013, 10:46 AM   #7
Jimro
Senior Member
 
Join Date: October 18, 2006
Posts: 7,097
Quote:
So, by math, the difference would be .2 feet of difference in drop. That's what I needed to know- thanks folks!!
It means that the angular correction is only .2 feet. The difference in bullet drop over .2 feet is smaller than I care to calculate, but I'm sure it is less than even the adjustments of the finest 1/8 MOA scope.

Just zero as normal.

For what it is worth, whenever you shoot uphill or downhill, you don't get into "interesting" differences in bullet impact until you are more than 25 degrees of slope, which gives you a 10% reduction in range to correct for. Which means at 1000 yards, with a 25 degree slope, you would use your 900 yard zero.

At short ranges and small angles, it really doesn't matter. In fact, anything inside your point blank range is "point and pull" no matter the angle, if you use a +/- 2" pbr zero.

Jimro
__________________
Machine guns are awesome until you have to carry one.
Jimro is offline  
Old July 1, 2013, 08:28 PM   #8
shredder4286
Senior Member
 
Join Date: May 13, 2010
Location: NE Washington
Posts: 361
Quote:
It means that the angular correction is only .2 feet. The difference in bullet drop over .2 feet is smaller than I care to calculate, but I'm sure it is less than even the adjustments of the finest 1/8 MOA scope.

Just zero as normal.

For what it is worth, whenever you shoot uphill or downhill, you don't get into "interesting" differences in bullet impact until you are more than 25 degrees of slope, which gives you a 10% reduction in range to correct for. Which means at 1000 yards, with a 25 degree slope, you would use your 900 yard zero.

At short ranges and small angles, it really doesn't matter. In fact, anything inside your point blank range is "point and pull" no matter the angle, if you use a +/- 2" pbr zero.

Jimro
Ok. 10% reduction in range for 25 deg slope. Putting that one in the "gun notes" file. Thanks for the info. Got more than I expected out of this one.
shredder4286 is offline  
Old July 1, 2013, 08:59 PM   #9
Art Eatman
Staff in Memoriam
 
Join Date: November 13, 1998
Location: Terlingua, TX; Thomasville, GA
Posts: 24,798
Just remember that in the common hunting distances, even ten percent doesn't have much effect on trajectory.

If you're sighted in for 200 yards, the usual drop for most deer cartridges at 300 yards is about six inches.

The drop at 270 yards would be around five inches. The one-inch difference is hardly worth worrying about.
Art Eatman is offline  
Old July 2, 2013, 08:23 PM   #10
shredder4286
Senior Member
 
Join Date: May 13, 2010
Location: NE Washington
Posts: 361
Quote:
Just remember that in the common hunting distances, even ten percent doesn't have much effect on trajectory.

If you're sighted in for 200 yards, the usual drop for most deer cartridges at 300 yards is about six inches.

The drop at 270 yards would be around five inches. The one-inch difference is hardly worth worrying about.
Hey, absolutely, Art. That being said- my rifle isn't even being sighted in at a 25 degree slope, so it's even less than a 10% decrease. I just thought it was interesting to know the actual mathematic equation to figure out what I needed to know.
shredder4286 is offline  
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 06:29 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2021 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Page generated in 0.08384 seconds with 10 queries