What a DOPE card is, and what it isn't
DOPE stands for Data On Previous Engagements. It's a small table that tells you how much to dial or hold for elevation and wind at each distance, for one rifle shooting one load. Most shooters tape it to the stock, keep it in a scope-cap holder, or wear it on a wrist coach.
The important word is previous. A card computed by a ballistic calculator is a prediction. It becomes DOPE once you've confirmed it with real impacts at real distances. Until then, treat it as a starting point.
What you need before you start
- A confirmed zero. Everything on the card is measured from it. Most precision rifles are zeroed at 100 yards (or 100 meters); hunters sometimes zero at 200. Whatever you pick, confirm it on the day, with the ammo the card is for.
- Your scope's units and click value. MOA scopes usually click in 1/4 MOA; mil (MRAD) scopes usually click in 0.1 mil. Build the card in the same unit as your turrets and reticle. Mixing them is the classic way to miss by a lot.
- Sight height: the distance from the center of the bore to the center of the scope. Measure it rather than guessing; it matters most at short range.
- Muzzle velocity from a chronograph if you have one. The number on the ammo box was measured from a test barrel and is often off for your rifle.
- Bullet weight and ballistic coefficient (BC). Use the manufacturer's published value; for long range, a G7 BC usually matches modern long-range bullets better than G1.
- Your usual conditions: altitude or station pressure, temperature and humidity where you shoot.
Step 1: Generate a starting table
Put those inputs into any ballistic calculator and generate a table at the distances you actually shoot: every 100 yards out to your limit is common, or every 50 if you shoot unknown-distance stages. For each distance you want three numbers: elevation (how far to dial up from your zero), wind (how much to hold or dial for a given crosswind) and, if you like, time of flight, which helps with moving targets and reading wind.
Keep the card short. A table you can read in two seconds behind the rifle beats a complete one you can't.
Step 2: Lay out the card
A typical card has one row per distance. Here's an example in both units for a 6.5 Creedmoor, 140-grain ELD Match load at 2,710 fps (G7 BC 0.326), 100-yard zero, 1.7-inch sight height, 1,250 feet and 68°F. These are calculated values from our own example card, not confirmed DOPE for your rifle.
| Distance | Elevation (MOA) | Elevation (mil) | 10 mph full-value wind (MOA) | 10 mph full-value wind (mil) |
|---|---|---|---|---|
| 100 yd | 0.0 | 0.0 | — | — |
| 500 yd | 9.85 | 2.87 | 2.6 | 0.76 |
| 1,000 yd | 29.35 | 8.54 | 6.0 | 1.75 |
Two conversions are worth knowing. One mil equals about 3.438 MOA, so 9.85 MOA ÷ 3.438 = 2.87 mil. And to turn a correction into clicks, divide by the click value: 9.85 MOA on a 1/4-MOA turret is 39.4 clicks, so you'd dial 39 or 40; 2.87 mil on a 0.1-mil turret rounds to 29 clicks.
Writing the wind column
Wind on a card is usually given for a full-value crosswind, meaning wind blowing at 90° to the line of fire. You can write it for 1 mph (multiply by the wind you call) or for a round number like 10 mph (scale up or down). For wind at an angle, the crosswind part is the wind speed times the sine of the angle: a 10 mph wind at 30° to your line of fire gives about 5 mph of crosswind, and at 60° it gives about 8.7. Many shooters simplify that to "full value" and "half value" by clock position. Use whichever you'll do reliably under time pressure.
Conditions belong on the card
Air density changes how fast a bullet slows down. Colder, denser air means more drop; warmer, thinner air means less. Write the conditions the card was built for (altitude or density altitude, temperature) in the header, so you know when it no longer applies. If you shoot in very different seasons or elevations, make a second card rather than stretching one.
Step 3: Verify at distance (truing)
This is the step that turns a printout into DOPE. Calculators are very good, but they're only as good as their inputs, and muzzle velocity and BC are rarely exactly what you entered.
- Confirm your zero first, on the day, in calm conditions if you can.
- Shoot a mid-range distance, for example 500 or 600 yards, while the bullet is still well above the speed of sound. Dial the card's elevation and fire a small group. Measure where the group's center lands relative to your aim point, not where a single shot went.
- If the group is consistently high or low, adjust the muzzle velocity in your calculator until its predicted elevation matches the real one. Velocity errors show up first at mid-range.
- Then check the far distances. If mid-range now matches but long range is still off, the BC is the more likely culprit. Adjust it until the prediction matches the impacts.
- Record what you actually used. If 800 yards took 18.25 MOA instead of the predicted 18.0, the card should say 18.25. That's what "previous engagements" means.
Before you blame the calculator, check the scope. Turrets don't always move exactly what's printed on them. A tall-target test, where you dial a known amount and measure how far the impact actually moved on a tall target with a measured line, tells you whether 10 MOA on your turret is really 10 MOA.
Keep notes as you go
Each time you shoot at distance, write down the distance, what you dialed, where it hit, the wind you called and the conditions. A few sessions of that is worth more than any calculator setting, and it's how you'll spot a load or a barrel changing over time.
Common mistakes
- MOA card on a mil scope, or the other way round.
- Using box velocity instead of a chronographed number.
- Building the card for one lot and shooting another. Velocity can shift between lots of the same load. Re-check when you change.
- Forgetting the zero has moved, after a scope remount, a cleaning, or a knock in transit.
- Over-trusting the far rows. The further out, the more small input errors add up. Long-range rows need the most verification.
Building and keeping your cards in GunCollector
GunCollector builds a DOPE card from the rifle and ammo you've already recorded: the barrel, twist and sight height from the rifle, and bullet weight, BC and velocity from the ammo lot, including published specs fetched from the manufacturer where GunCollector supports it. It generates elevation and wind for every distance in MOA or mils, and every row stays editable so you can write in your confirmed numbers after a range day. The cards are on your phone and readable with no signal, so they're with you at the bench. The step-by-step version with screenshots is in how to build a DOPE card in GunCollector.