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If you are reading this thread, you have probably heard the term DOPE.
It's just another military Acronym for "Data Observed from Prior Engagements".
In the precision rifle world, we might also say it means "Data Obtained from Previous Experience".
Either way, it's information about how your gun/ammo performs in a given set of conditions.
Hard Dope vs. Soft Dope.
There's two kinds of dope, hard and soft.
Hard dope is information YOU gathered in a specific set of conditions.
Soft dope is information simulated by a computer or arrived at by estimating or approximated from other sources of dope.
It's always best to have hard dope for the conditions and location you are shooting in, but it requires shooting a LOT in order to get good dope for every set of conditions in every location.
For most of us, we will work from a combination of hard dope and soft dope with corrections.
Zero you rifle.
Believe it or not, your zero will change with the conditions.
Just because your gun was zeroed perfectly the last time you shot it, don't assume it's still perfectly zeroed when you arrive at a new range with drastically different conditions than when your gun was last zeroed.
When you come out to one of our CaPRC clinics, we start by getting a solid 100yd zero.
This is most important because you are building your dope FROM the 100yd zero.
A 100yd zero range is universal across the USA and almost any range you visit will have a 100yd range available for you to check/adjust your zero.
Once you have a good zero, re-adjust your turrets so they are reading zero.
If you choose not to adjust your zero, you MUST account for any necessary corrections when you start shooting at distance.
Record your Conditions.
Gathering dope without knowing the actual conditions will not help you much.
You need to be observing the barometric pressure and the temperature at the bare minimum.
This usually means purchasing a handheld weather meter.
They are available starting around $100.
If you don't have one, at least track the altitude and temperature.
Then you can go online and find the observed pressure and temperature later to add to your records.
The reason you need to track the pressure and temperature is that these two factors change the density of the air.
The density of the air directly changes how much your bullet drops as it heads towards the target.
Record your come-ups.
You will gather your first hard dope by firing at a target and observing the impact.
Let's say you are shooting federal gold medal match 308 with the 168gr sierra matchking bullet.
The federal graph shows you drop in inches which is just about worthless, but with some simple math, you figured out that the 26" of drop at 400 equates to about 6.25moa of drop.
So, you dialed 6.25moa on your scope and you fire a round.
The bullet hits the target, but it landed 2" high.
So, you can now observe that 6.25moa was close, but not perfect.
In precision rifle shooting, we want every shot to be perfect so you make a 1/2moa adjustment down for a net 400yd come-up of 5 3/4moa.
Now you fire another round.
This one lands right where you aimed it.
Record that 5 3/4moa as your 400yd come-up for today's conditions.
Continue this process until you have at least 3-4 different distances logged that span the usual distances you expect to be shooting.
Let's say you plan to shoot to 600yds.
You would want to gather hard dope for 300, 400, 500 and 600.
Having perfectly even distances are not important as long as you record WHAT the distance was and WHAT the come-up was for that distance.
Check your velocity.
Don't rely on the velocity figures on the end of the ammo box or the reloading manual to actually be true in YOUR rifle.
They may be close, but will rarely be perfect.
Beg, borrow or steal a chronograph and check your ammo in your rifle.
Record this velocity and also note down the temperature at which you fired the test rounds.
It's quite common to see higher velocities on hot days.
We usually have a chrongraph available at CaPRC clinics.
Remember that the bullet comes out of the barrel a couple inches below your line-of sight to be sure you are holding several inches above the chronograph so you don't shoot it!
Working with your dope.
Now that you have a good idea how your bullet performed in the conditions you were shooting, it's time to extrapolate how it would perform in different conditions.
You begin by working with the ballistics program of your choice and entering your bullet, measured velocity and the weather conditions you recorded.
Run a bullet drop chart and see what it says.
If you are lucky, the data will match what you recorded by actual firing.
You will rarely be lucky.
Before you can use a ballistics calculator to reliably simulate data in un-tested conditions, you need to fool it to simulate data that matches your hard dope in the same conditions it was gathered.
Using our 400yd example above, you want the program to be telling you 5 3/4moa of drop.
If the computer is telling you something different than what you observed to be true, then you can't trust it.
The trick is to change the BC figure around until you get the computer data (soft dope) to match your hard dope.
Once you arrive at the correct BC to use, record that figure.
You should then be able to use that BC and your measured velocity to make sucessful simulations for other weather conditions and locations.
Creating new Soft Dope.
Let's say it's time to go to a new location for which you have no dope.
Obtain as much information ahead of time as possible as far as what the altitude and weather is like.
Enter this into the ballistics calculator and use your known-good BC and velocity to generate your range card.
Now go shoot at the new location.
As before, record the actual conditions and make notes on your dope card what corrections were necessary.
You will usually be able to see a pattern of corrections on the day of shooting.
For example, the last time I shot at Sacramento, my 500yd dope was about 1/2moa off.
Then my 800yd dope was 1moa off.
I was not suprised at all when I needed to adjust my 1000yd dope by about 2moa.
I even put this correction on the scope before firing my first rounds at 1000yds and it turned out to be correct.
More on pressures.
Within the same weather system, pressure changes dramatically with altitude.
If you only shoot at one location, this won't be as important for you as your dope won't change as much as if you are shooting in different locations with drastically different altitudes.
You should not rely on the barometric pressure you hear on the news as that is corrected for sea level.
For best results, you want to have the ACTUAL barometric pressure where you are shooting.
However, many ballistics programs will allow you to use sea-level-corrected pressure as long as you also input the altitude.
When you have the absolute pressure (also called station pressure), you should not input the altitude into the ballistics software. Instead, use an altitude of sea level (0 ft) and use the actual pressure from where you are shooting.
Most balistic programs available to use on your cell phone can lookup your local conditions if your phone has a GPS built into it.
My ramblings on Density Altitude.
You may have heard about density altitude being used instead of barometric pressure and temperature.
Density altitude is a single figure that combines station pressure and temperature.
Density Altitude is based on the standard atmosphere model that meteorologists, pilots and ballistic calculators all use.
The standard atmosphere model states that there are standard conditions at different altitudes.
These conditions then corelate with a specific air density.
Therefore, we can also say that there are different air densities at different altitudes.
As we said earlier, air density directly correlates to bullet drop so we are most interested in knowing the air density that we are shooting in.
There's no way to actually measure air density in a handheld device, so we rely on the handheld weather station to calculate density from the pressure, temperature and humidity that can actually be measured.
The density is expressed as a density altitude.
Let's say you turn on your kestrel and it tells you that the density altitude is 1900ft.
What that means is that the air you are standing in right now (regardless of your actual altitude) has the same density as if you were at 1900 feet in the standard atmosphere model.
Density altitude is a very convienent way to log your weather conditions because it boils everything down to one figure.
You can even go so far as to generate a set of dope cards based only on density altitude.
Once you make, test and correct these cards, you can arrive at any location, turn on your kestrel and select the dope card that is appropriate for the moment.
Something else to note is that the conditions change throughout the day.
I usually see a 1000-2000ft density altitude change from morning to afternoon.
In my 308 data, I see that each 1000ft of density altitude change accounts for about 1moa of elevation adjustment at 1000yds.
What this means is that you really need to stay on top of the weather conditions and be using the correct dope for the MOMENT, not just the day.
_________________
God shoots a Remington 700, drives a Chevy Truck and carries a Glock 19.
I don't do any of those things.
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