Location: The rifle range, or archery range or behind the computer in Alaska

Posts: 3,740

Re: Long Range Incline and Declined Angle Shots

Quote:

Originally Posted by SBruce

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.

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.

__________________
__________________
Long range shooting is a process that ends with a result. Once you start to focus on the result (how bad your last shot was, how big the group is going to be, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.

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.

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.

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.

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.