We’ve covered a lot of material on long range shooting thus far, and now we’re ready to start implementing some of what we’ve learned, starting with ballistic tables. But first, what is a ballistic table, and how do you read one? Let’s dive in.
A ballistic table (also called ballistic chart, ballistic card, or data card), is a table containing a set of data regarding the external ballistics of an ammo or, to be more precise, of a particular bullet fired in particular conditions. The data contained in the table allows you to easier calculate the sight adjustments needed to shoot at distances, or conditions, different from the zero range or zero conditions.
Ballistic tables are arranged in rows and columns, and the contained data (and their disposition) vary in function of the needs of the creator and the software used to create them. There are, however, elements common to every table that are essential to every shooter. Following along with this guide, and through your own experience, you will find what you need in your tables and how to arrange the data to best suit your needs.
In this post, we’ll analyze a ballistic table created with the online software JBM Ballistics. (I’ll go into further detail with using this software in a future post.) The table is on the picture to the right, and you can enlarge it to its original size by clicking on it.
Among the input data, you should be able to recognize most of the terms that we have discussed in previous articles. For now, we are going to concentrate only on the specific information that we need when actually using the ballistic table. They are:
The data relative to the bullet, i.e., manufacturer, caliber, weight, ballistic coefficient and muzzle velocity. In this case, the table is for a .308 caliber 175gr Sierra MatchKing bullet, with a ballistic coefficient of 0.243 (relative to the drag function G7, in ICAO standard atmospheric conditions). The muzzle velocity, measured at 10ft from the muzzle, is 2700fps. “Litz” means that Brian Litz has calculated and tested the G7 BC for that bullet (generally a more accurate and reliable result than the standard G1 BCs declared by Sierra and the other bullet makers).
The data relative to the ambient conditions for which the table has been calculated, i.e., temperature, pressure, humidity and altitude. In this case, the table has been calculated for a temperature of 59°F, a pressure of 29.92 inHg, a percentage of humidity of 0%, and an altitude of 0ft (that is, at sea level).
The data relative to the wind speed and direction for which the values of windage have been calculated, in this case a wind at 10mph from 90° (that is, perpendicular from the right).
The data relative to the target speed and direction at which the values of lead have been calculated, (useful when shooting at a moving target) in this case a target moving right to left (perpendicular to the line of sight) at 10mph.
We can now analyze the ballistic table. As you can see, the rows list the range distances, from zero to 1000yd, in 50yd increments. On the columns are all the values with the relative unit of measurement. Starting from the left, you can find:
Range (yd), which is the range in yards from the shooter to the target. The marked row, in this case 100yds, is the zero range.
Drop (in), despite being called “drop”, it actually is the bullet path, since it is relative to LoS (line of sight). It is the correction, in inches, that you need to hit the target at the various distances when your sights are set for zero range.
Drop (MOA), is the amount of adjustment you need to set on your scopes turret, calibrated in fractions of MOA, to compensate for a particular distance different from zero range.
Windage (in), is the amount of drift in inches, at the various distances, due to the wind of 10mph from the right. Unlike drop, it is does not refer to zero range.
Windage (MOA), is the amount of sights adjustment you need to set on your scope to compensate for a wind of 10mph from the right.
Velocity (ft/s), is the residual speed, in feet per seconds, of the bullet at the various distances. The marked row, in this case an additional row corresponding to 1028y, corresponds to the sound barrier crossing. Notice that it is the sound barrier that has been marked, not the transonic region.
Mach, is the bullet speed relative to the speed of sound. Here again, this row is denoted relative to the sound barrier crossing.
Energy (ft*lbs), is the residual kinetic energy of the bullet, expressed in feet per pounds. It is useful for hunting and military purposes to predict the bullet wound effect.
Time (s), is the time of flight of the bullet (in seconds).
Lead (in), is the amount of lead, in inches, that you need to hit a target moving perpendicular to the LoS at 10mph.
Lead (MOA), is the amount of adjustment you need to set on the windage turret of your scope, to hit the moving target aiming dead center instead of aiming in front of it.
An important thing that must be considered when dealing with a ballistic table, is the zero range. Indeed, the values of drop always refer to that particular distance. To properly use the ballistic table, your sights need to be zeroed for that range.
If it’s not specified in the table header, like in the example presented above, you can obtain the zero range just looking for that range where drop is equal to zero. Windage is often absolute, in other words not relative to zero range, so don’t use it as a reference to find zero range.
Another thing to consider is that the values present in the ballistic table are, as you can see, for limited distances and wind conditions. If you need the correction values for distances or wind conditions not listed in the table, you will need to calculate, or estimate, them using the closet values available.
In the next couple of articles, I’ll start to talk about how to set up and zero your weapon system, and how to collect the necessary data to create your own ballistic table. These will be your very first steps toward your perfect, one shot hit, long range shot. I will also start posting articles about how to properly set up a long range rifle, how to improve its inherent accuracy, how to select the best riflescope for your needs, and how to select the proper ammo. There is still a lot to talk about, so stay tuned guys!
The featured image, courtesy of Snipercentral.com, is an example of standard pre-compiled ballistic table that you can find and buy in specialized stores.