The questioned asked all the time when it comes to Angled Fire; “Where do I hold” ? The average shooter will know, whether shooting up an incline or down, there is a noticeable offset. The biggest point of confusion is, “do I hold high or low” and “is it different depending on the direction of the fire” ?
The short answer is no, there is no difference. Regardless of whether you are shooting up or down, the answer is Hold Low. But because of the potential
variations in the shot, we need to know by how much.
Why do we hold low, gravity. In both cases, gravity will have less of an effect on the bullet as it is not covering as much flat line distance. Do demonstrate this we have a simple diagram. With 3 equal distance lines.
There are several methods to determine the offset, and before we continue, I want to state up front, there are small variations when it comes to shooting up hill vs downhill. That same effect from gravity will help or hinder the bullet’s flight, but for all practical purposes it’s not enough to worry about. You can research it and Sierra has a great exterior ballistic article on Inclined Fire from William McDonald. These were written in 2003 and do an awesome job explaining the math behind it all. He goes in to much more detail than necessary, but it’s worth a read.
Practical Field Application
In the field a good shooter will maintain around 2 MOA of accuracy. This has been proven in numerous competitions, and field exercises. We can shoot really
tiny groups all day long on the square range, but hit the woods things change dramatically. We are no longer controlling the situation, as an example, we
will probably have to engage the target from an alternate position. (Something other than prone) This fact, plus a few more add up to roughly 2
MOA of expected accuracy.
My first point when talking field work, specifically angled fire, is that most angles are found in the mountains. We have to physically get to our firing position. That can take a bit of effort on our part.
With inclined fire, we don’t have to worry about angles smaller than 10 degrees. While distance will certainly increase the offset, an angle of less than 10 degrees is well within our accuracy standard. So to find these larger angles, that usually means mountains. We’d be hard pressed to find an 800 yard shot at a 30 degree angle in Florida.
How we physically conditions ourselves, the ability to feed our body properly matters. If you're out of breath and trying to move rapidly to a firing
point, you’ll feel it. Especially if you are a flat lander. Consider those people on their first hunting trip to Rocky Mountains. They flew in from the
East Coast, didn’t take the time to acclimatize to the elevation and now need to get up to 9,000ft in order to bag that trophy elk. The altitude will
matter, so think it about it ahead of time.
There is a lot more of the shooter involved in the field then what you might see with a benchrest set up. We are the support system, so what is going on with us will translate through the rifle system. Very few courses on inclined shooting mentions this, but trust me when I say, it matters. If you take one, you’ll find out fast what you level of conditioning is. I recall one such class where the students were unloading all their cool guy toys after that first day, only bringing the essentials.
Down to the math
Ok, enough of that, let’s talk about shooting and the offsets. We have two “Rule Of Thumb” adjustments that you can use. The Rifleman’s Rule and the Improved Rifleman’s Rule. Both are very similar to each other, but they address two different aspect of the shot.
The Distance vs the Dope ?
The Rifleman’s Rule
states you take the straight line distance to the target, say, 800 yards and multiple it by the cosine of the angle measured. So if the cosine is .85,
you’d use 85% of the measured distance to target. (Roughly a 30 degree angle)
800 yards X .85 (cosine) = 680 yards.
Instead of shooting the target with your 800 yard dope on the rifle, you’d use your 680 yard dope instead. Pretty simple.
The Improved Rifleman’s Rule says virtually the same thing, but instead of taking the cosine of the distance you would take the cosine of the dope used.
25 MOA X .85 (cosine) = 21.25 MOA
7.2 Mils X .85 (cosine) = 6.1 Mils
How we derive the cosine is by using a Sniper Tools Cosine Indicator.
I will note that you can buy a cosine indicator with degrees, but getting one with the cosine is much easier and cuts a few step out. When you are in the field, it’s best to keep it simple.
Some Real World Numbers as an example.
The straight dope for my GAP Gladius shooting 175gr OTMs @ 2575fps is;
800 yards = 7.1 Mils / 24.5 MOA
So let’s look at these Rule of Thumb formulas below, before letting the computer do it.
800 yards = 24.5 MOA / 7.1 Mils
680 yards = 18.6 MOA / 5.4 Mils
24.5 MOA X .85 (cosine) = 20.8 MOA / 6.0 Mils
Computer Determined w/ Angle from Ballistic Program
20.5 MOA / 5.9 Mils
The closest to the ballistic program is the Improved Rifleman’s Rule with 20.8 vs 20.5 MOA.
These results are determined with verified data in our ballistic program.
So we have a .3 mil variation or a 1.6 Mil variation which is big. 8.6” vs 46”.
While computers make the job much easier, using the right tool like the Angle Cosine Indicator is a battery free solution and just as easy. It comes down to the percentage of the dope used. Especially if it is cold or you have been out all day in a location without a cell signal. You might run into a battery issues, so having a mechanical back up is worth it’s weight in gold.
Remember, the greater the angle, the longer the distance, the bigger the offset will be. Another important point to remember is; The Wind.
We still have to Dope the entire straight line distance for the wind. The wind is not given an offset like the drop is. So if you have an 800 yard shot, you use the dope for your straight line distance when it comes to figuring the wind. Don’t use the 680 yard wind call, or any other variation, use the full value.
A lot of people experience this for the first time when it counts. Being armed with the correct information up front is valuable. Don’t go on that hunt of a lifetime without being armed with the right information.