Long Range Incline and Declined Angle Shots

[Michael Eichele]

When your indicator reads 96, how is that supposed to be used? Are you supposed to dial 96% of your normal dope?.........I've never used one like that.

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Pretty much. This is the improved rifleman method. If you are shooting on a 30 degree slope, you would take .866 * your drop. Inches, MOA, MILS etc....So say your drop is 92" at your intended target's range and the slope is 30 degrees. 0.866 * 92" = 79.7". This still isnt quite as accurate as using the baseline drop but gets the job done for most hunting situations and is a HECK of a lot more accurate than using a given line of sight range * the cosine value.

 

[SBruce]

CA48,

Not trying to hyjack this thread, just trying to give a detailed answer to the best ways of compensating for angled shots. Alot of people have these indicators on their guns but don't fully understand how to apply the data and get the most accurate corrections. I've used the Sierra calculation (that Michael gave) ever since the rockchuck lesson. Passing it on helps me remember it too. They say we learn best by teaching others.


sp6X6,

I can see how you use the cos indicator to come up with the same correction as using an angle indicator. I'll edit my earlier post. They both work as long as the math is done proper. Sorry for any confusion.



Ok fellas, I did all the math and checked it against the NF ballistic program more than once.

My PC version asks for the incline angle, not the cosine, so I'll refer to angle.

Based on 30 degrees vs level, here's what I came up with.

First, the new correction can be calculated and applied without a field ballistic program, we need an indicator of some sort and a basic scientific calculator.

We would need to have the total drop at X distance written down and the M 2 Z (correction needed) at X distance on level ground recorded too.

As already discussed, the Cosine of Angle times LOS distance doesn't work very precisely, but it is one of the simplest and fastest way to compensate to an extent.

The Cosine of Angle times correction on level ground doesn't work either, because our correction for distance never matches total drop. however, the closer the two numbers are to each other, the better this method could possibly work (one reason to zero at 100 yds and use a low mounted scope maybe).

Now this leaves two methods that match the ballistic program precisely.

1) 3 step manual calculation: Read the Cos or angle value from indicator and multiply by total drop at X distance. Subtract this number from the total drop. Subtract this new number from the level ground correction for same X distance.

(Cos 30 X 51.1 = 44.3) (51.1-44.3 = 6.8) (33.4 - 6.8 = 26.6)
Where 30 is angle, 51.1" is total drop at 500 yds, 33.4" is correction on level ground at 500 yds, and 26.6" would be the new correction for the 30 degree angle at same 500 yds.



2) Another manual calculation: Read the Cosine or angle value from indicator and Subtract it from 1 (1-CosA). Multiply this number by total drop at X distance. Subract this new number from the level ground correction for same X distance.

(51.1 X (1-Cos 30) = 6.8) (33.4-6.8 = 26.6)
Where 30 is angle, 51.1" is total drop at 500 yds, 33.4" is correction on level ground at 500 yds, and 26.6" would be the new correction for the 30 degree angle at same 500 yds.

Or, as Michael wrote: 33.4-(51.1(1-Cos30)) = 26.6" at the same 500 yds.

The second calc is simpler than the 1st with a basic scientific calculator, less key strokes. Third example is faster still.
Either one could be done with a basic spreadsheet app if you don't have access to a field ballistic app too. But I am not the person to design the spreadsheet, I understand the trig way more than I understand a computer, LoL.

 

[Don Ward]

For those getting painful flashbacks of math class finals the morning after the big party at the Johnson twins' house, try this:

30deg incline = reduce yardage by 10%

20 deg incline = reduce yardage by 5%

Under that just shoot and keep your knife sharp

Over that...see above posts

Its not exact, but you can do it in your head quickly when hunting and it handles out to medium ranges in most terrain with a flattish round. 30 deg is actually pretty steep and to get 30+deg and a really long opportunity takes some serious terrain.

 

[rscott5028]

It's actually nice to have both the precise formulas as well as a rule of thumb that can be applied quickly in the field.

Thanks All!!!

 

[CA48]

SBruce not to worry. Before this this thread I was only aware of the Basic Riflemen method. Seeing all these examples makes things much less complicated.

 

[sp6x6]

Don, In agreement on terrian, I was going to post pict, but cat get it for some reason. I hunt some extreme steep and cliffy areas, seems like wolfs are pushing them into harder areas. Few years back I was in a steep canyon, and came across a couple bulls, buddy was spotting, not far 502 yrd. Well, it was last aftrnoon,last day,and I WASNT thinking right, had no angle finder, Knew it was steep, I shot, he said I MISSED, HE was spotting for a friend also, two bulls. I got back on target and just a leg was sticking up in the air. Not the reaction of a low chest shoot.shot was about a 350 hold, checked some years later.I have hunted same spots for 20 yrs. and I AM IN PROCESS, of making notebook of chutes,etc,landmarks,for refernce. I have shot game or bears in much of the area already, Going to have a cheat sheet for my favorites. I did this where I road hunt High country on days off from hiking, picts w/ notes.We have fog and snow alot, hard to lazer.

 

[Buffalobob]

Made two shots 3 inches apart at 968 yards on a 6X6 elk with this type of angle and setup.

The actual picture is of a shot I did not take on a 3X3 at 1760 yards. Reason I did not fire was a swirling unpredictable wind.

 

[Michael Eichele]

This is my steepest shot. 702 yards near 45 degrees. Notice the tripod under the rear stock......

 

[rscott5028]

Great photos Buffalo and Michael!!

45 degrees around here will get you about 25 yards to the bottom of the arroyo.

thanks for sharing!

 

[rscott5028]

On Long Range Pursuit tonight, Aaron Davidson gave some shooting tips for "Fisting your Incline". It sounds pretty easy and might be worth the practice in case all of your instruments break down.

I'm not sure I can describe it adequately, but you essentially make a fist and hold it out horizontal. The bottom of your fist is essentially 5 degrees down. Rotate your fist down one time and you're at 10 degrees. Rotate back the other way heading down once more makes 15 degrees and so forth.

Once you have a good guestimate of the incline/decline, you can apply the rules that others have discussed above in order to compensate.

Not sure if anyone above mentioned it. But, you shoot to the adjusted distance as pertains to trajectory/elevation. And, you hold for wind for the full distance of the shot.

...better than a stick in the eye

 

[horse2960]

I need a little help from you angle shooters out there. I have been playing around with my 338 edge for a while now out to 1,965 yds on a regular basis and still have a lot of learning to do. I understand the effects of weather conditions, spin drift, and the lesser effects from Coriolis, ect... But all of my shooting has been from for the most part level ground. I may have a new shooting spot but there is going to be a lot of inclined angle shots. So how does this work figuring in with your regular drop. Do you get your angle while your aimed at your target before adjusting for drop with something like a protractor with a level. Then get the cosine for that angle and times it by the ranged distance to get your new distance or am I way off here?

I have been trying to get an answer on this subject as well. there is so much miss information out there it isn't funny. You should read Arther Pejsa' book Modern practical Ballistics with a short chapter on uphill/down hill shooting . He explains that the bullet is effected by gravity by time in flight not horizontal distance. that myth has been around for a long time. Cos of the angle doesn't work perfectly eather especialy for the ranges you are talking about. for example if I shoot 800 yds at 30 degrees figure out the cos of 30 at 800 which would be 693yds dial your scope and shoot, based on Pejsa ballistic program you would hit 9.8 inches low with my atmospheric conditions that I entered- that is unacceptable erorr . that is why I wont use cos past 400yds . rememder the bullet is falling faster and faster the longer it is in the air plus the bullet is going slower and slower compound the two and you need to do a lot of math to accuratly figure things out. I would be glad to run some data for you with Pejsa' program.

 

[rscott5028]

[...]He explains that the bullet is effected by gravity by time in flight not horizontal distance. that myth has been around for a long time.

It's not a myth. It's simply a matter of perspective and which variable is easiest to key in on for determining an acceptable shooting solution in the field.

Sometimes a yard stick works and sometimes you need a micrometer.

The better choice is the one that gets the job done. Not necessarily the one with the best precision.

Even you implied that you would use cos out to 400yds.

[...] rememder the bullet is falling faster and faster the longer it is in the air plus the bullet is going slower and slower compound the two and you need to do a lot of math to accuratly figure things out. [...]

It seems like you just contradicted Pejsa and Newton. The bullet falls at the same rate through the entire flight path... 9.80 m/s^2. It simply covers less terrain as the forward velocity decreases.

You can twist things around by firing straight up and the bullet isn't falling at all for about half of its journey. Then, it falls at an increasing rate until it reaches terminal velocity and doesn't fall any faster.

All of the banter is useless for hunters if there's no practical application.

-- richard

 

[Buffalobob]

The bullet falls at the same rate through the entire flight path... 9.80 m/s^2.

What does "rate" mean. A bullet has velocity and it has acceleration. You quote an acceleration which means the first derivative i.e velocity, is a variable.

All of the banter is useless for hunters if there's no practical application.

You should buy Brain Litz's book and read it.

 

[rscott5028]

What does "rate" mean. A bullet has velocity and it has acceleration. You quote an acceleration which means the first derivative i.e velocity, is a variable.

You should buy Brain Litz's book and read it.

Bob,

You're right. Reading the book is far more productive than stirring the pot here.

Either way, I have no problem with a rule of thumb or oversimplification that yeilds good results. One just needs to keep in mind the limitations.

thanks!
richard