Sighting in a rifle on unlevel ground

[backstrap]

Would u sight a rifle shooting down hill100 yards if so would the zero hit in the same place if u where shooting on a 100 yard flat ground its not like its a real step hill or incline  but u are still shooting down hill so i was just wondering what u all think about this ?? i have a guy that lets me sight my guns on his place that has a 100 yard place i can shoot thats down hill some or another guy that has a flat place i can shoot out to 500 yards thats all flat but the guy with the hill ground is closer to where i live than the flat ground

[Spanky]

I sighted in my .223 bull barrel in my backyard which is a slight uphill. When I shot it at a flat range it was way high.

Spanky

[Jimbo47]

It does make a difference, and how much of a slope is going to determine how far off the shots will be!

I used to shoot at a place that had targets slightly uphill, and my shots on level ground would hit about an inch or so different from the uphill shot.

If you know how much the variation will be between shooting level and elevated then all you need to do is make allowance for it the next time you use the range.

[McLernon]

Up to a slope of + or - 6 degrees from horizontal  it shouldn't make any difference at all because by trigonometry the hypotenuse is equal to the adjacent to three or four decimal places. In other words 6 degrees is mathematically secondary.

Mc

[cascadedad]

Shooting 100 yards at 45 degrees (up OR downhill) is equivalent to shooting 70 yards on flat ground.  45 degrees is STEEP.

Shooting 100 yards at 20 degrees is equivalent to shooting 94 yards on flat ground.  Or shooting 300 yards at 20 degrees is equivalent to shooting 282 yards on flat ground.

IF you want to shoot at a 100 yard equivelent at the 20 degree slope, you would only have to extend the range to 106 yards.


Spanky, something else must have been going on with your 223, i.e. your rest, different ammo, or something.  If you sight dead on shooting either uphill or downhill and then move to a target at the same distance on flat land, you should hit low.......not high.  Can't mess with physics.

Think about shooting straight down or straight up.  The bullet would go in an absolutely straight line and would not "drop". 

[Spanky]

When I sighted in my .223 in the backyard I was only shooting at 40 yds or so. I just wanted to get it in the ballpark. When I went to the range I was shooting at 100 yds. The slope in my yard is probably about 25% grade.

I dont know exactly why but it was shooting high at the 100 yd range.

There is one difference though, when I shot in the yard, I was shooting off a my porch railing and when I shot at the range I was using a bipod on the gun.

I dont know if that makes a difference or not but it's all I can think of.

Spanky

[Fred M]

Quote.

The slope in my yard is probably about 25% grade.

25% grade or slope is not 25deg.  25% grade is 11.25deg. % of slope is not much use unless you know how to convert % into degrees.

If you are shooting 350yrds up or down hill at 100% grade your rifle will impact as so you were shooting at 247 yrds or aim as you would at 247yards.

When hunting in the mountains with a flat shooting rifle for big game like goat or sheep, with a point blank range of say 350yrds with 5" radius at 350 you don't need
to worry too much about hold under even at a 45deg angle. You should however carry a  Silva compass with an inclinometer and a range finder of sorts to take out
the guess work.

cosin of angle x slope length= level shooting distance. Or 11.5deg slope angle cosin=.9799x350=342.9 yards. As can be seen the difference in aim is very little at that angle. I used a sticker on the stock with some angle data.

[Mac11700]

You should however carry a  Silva compass with an inclinometer and a range finder of sorts to take out

Or for those who don't want to spend any money...they can make their own inclinometer...http://www.exploratorium.edu/math_explorer/howHigh_makeInclino.html ...

Mac

[Fred M]

Great tool a long as you don't get rained on. I stick with my Silva compass also
I have no more use for it since my mountain hunting is long past.

Some one is making a range finder with reads the slope angle and gives you
the horizontal distance with a build in cosinus function. It also has a mil scale. Made for extreme mountain hunting. How can you miss. One of these mini scientific calculators are also a great help to compute slopes, distances, river crossings, travel time etc.

Binocs with mill scales are also very useful, also hard to find.

[Mac11700]

Yup...Leupold makes that range finder with that feature...and I did see an old pair of Steiner binoculars with the mil-dots in them once a long time ago at a yard sale..at the time I didn't know what they were for...to bad...they were nice and clear

Mac

[edgemark]

When I sighted in my .223 in the backyard I was only shooting at 40 yds or so. I just wanted to get it in the ballpark. When I went to the range I was shooting at 100 yds. The slope in my yard is probably about 25% grade.

I dont know exactly why but it was shooting high at the 100 yd range.

SNIP

Your bullet will, when sighted in normally, cross the line of sight ( LOS ) twice. Since the sights are above the centerline of the bore, the bullet is fired at an upward angle and will cross the LOS, and continue to its max height above the LOS then cross back down.


Here is an example:
I sight my 150 grain 0.308 Accubond to be dead on @ 275 yards.

@ 26 yards it is dead on;
@ 150 yards it will be 3 1/2 inches high

If I were to Zero this to be Dead On @ 40 yards it will also be Zeroed @ 185 yards and will be 1 inch high @ 100 yards.

edge.