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 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.
 June 30, 2013, 01:21 AM #2 big al hunter Senior Member   Join Date: March 12, 2011 Location: Washington state Posts: 1,048 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!
 June 30, 2013, 05:14 AM #3 Jimro Senior Member   Join Date: October 18, 2006 Posts: 7,079 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.
 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: 1,599 No difference ! __________________ Don't forget to have your liberals spayed or neutered !
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!!

 June 30, 2013, 03:48 PM #6 WWWJD Senior Member   Join Date: February 9, 2011 Location: Central KY Posts: 542 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 fo Life Member
July 1, 2013, 10:46 AM   #7
Jimro
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Join Date: October 18, 2006
Posts: 7,079
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.

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.

 July 1, 2013, 08:59 PM #9 Art Eatman Staff Lead   Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 23,969 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. __________________ You're from BATFE? Come right in! I use all your fine products!
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.

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