G
Guide

How to Build a DOPE Card for Your Rifle

A DOPE card — Data On Previous Engagements — is the elevation and wind-hold cheat sheet taped to your stock or stuffed in your range bag. Building one by hand means a ballistics app, a manual entry of every field, and a printout. GunCollector builds it from data it already has: the rifle you added, the ammo you're shooting, and one click.

1. Add the rifle

From Collection, click + Add firearm and choose Take or Upload Photo. We're building this card for a 6.5 Creedmoor bolt-action, so that's the photo we uploaded:

The Add Firearm modal offering Take or Upload Photo or manual entry
Same entry point as any other firearm — photo first, details after.

The AI reads what it can from the photo and pre-fills the form. Confidence varies with photo quality and angle — here it came back at 35%, which is a normal result for a rifle photographed at a slight angle with no visible markings:

AI pre-filled fields from your photo banner showing 35% confidence, with a note to review and adjust as needed
Lower confidence just means more fields to double-check — nothing saves until you review it.

Everything below the banner is a normal editable form. We filled in Ruger / Precision Rifle / Gen 3, set Firearm type to Rifle, Action type to Bolt action, Caliber to 6.5 Creedmoor, and cleaned up the barrel length, twist rate, and chassis details to match. Click Add to collection and you land on the finished detail page:

Firearm overview page for a Ruger Precision Rifle Gen 3 showing Make Ruger, Model Precision Rifle, Caliber 6.5 Creedmoor, Action Bolt action, Barrel 24 inches, Barrel twist 1:8, and Optics ready Yes
Caliber, action, barrel length, and twist rate all carry forward into the DOPE card automatically.

Barrel length and twist rate matter here for reasons beyond bookkeeping — they're two of the inputs GunCollector's ballistics engine uses later, so getting them right on the firearm record saves you from re-entering them on every card.

2. Add the ammo — and pull real ballistics

A DOPE card is only as good as the ballistic data behind it. From the Ammo page, click + Add ammo and enter the load. We used Hornady's 6.5 Creedmoor 140gr ELD Match, part number 81500:

Ammo entry form filled in: Caliber 6.5 Creedmoor, Manufacturer Hornady, Brand/Line Match, Part number 81500, Grain weight 140, Bullet type ELD Match
Manufacturer and Part # are what power the ballistics lookup — same as adding any other ammo.

Open the ammo lot and click Find Specs. Hornady is one of the manufacturers GunCollector fetches directly from, so muzzle velocity, energy, ballistic coefficient, sectional density, and a full drop table come back in a few seconds — review the checkboxes and save:

Ballistic Specs section for Hornady 140gr ELD Match showing Muzzle velocity 2,710 fps, Muzzle energy 2,283 ft-lbs, BC 0.326 G7, Sectional density 0.287, and a six-row drop table from 0 to 500 yards
Real published G7 ballistic coefficient — the single most important number for a long-range DOPE card.

That G7 BC of 0.326 is doing a lot of work here. It's what separates a DOPE card that's actually accurate at 600–1000 yards from one that's just a rough guess extrapolated from a G1 number on the box.

3. Start a DOPE card

Open the rifle's detail page and click the DOPE Cards tab, then Create First Card. The wizard walks through five steps — Identity, Optic, Ballistics, Environment, and Review:

On the Identity step, name the card, choose your display unit (MOA or MRAD), and set the zero distance — we used a 100-yard zero. On Optic, enter your scope height over bore if you haven't linked an optic from Accessories yet; 1.4–2.0 inches is the typical range for a scope on rings.

4. Link the ammo and let GunCollector fill in the ballistics

This is the step that saves the most time. Instead of retyping bullet weight, BC, and velocity, just pick the ammo lot from the dropdown:

Ballistics step with Hornady Match 6.5 Creedmoor 140gr selected from the Ammo dropdown, auto-filling Ballistics Coefficient 0.326, Bullet Weight 140, Bullet Type ELD Match, Muzzle Velocity 2710, Barrel Twist Rate 8, and Barrel Length 24, each tagged 'from ammo record'
Every field tagged “from ammo record” came from the Find Specs lookup — nothing retyped.

Barrel twist rate and length are pulled from the rifle itself. Every value here is still editable — this is a starting point, not a lock — so if you're running a different lot with a chronograph'd velocity, you can override the manufacturer number.

On the Environment step, set the altitude, temperature, and humidity for where you actually shoot. These become the card's baseline; you can override them at generate-time later without changing what's stored:

Environment step showing Altitude 1250 feet, Temperature 68 degrees Fahrenheit, and Humidity 40 percent
Density altitude shifts your drop and wind numbers more than most people expect — worth setting for real.

5. Generate the table

Click Create Card and you land on the card with an empty row table and a summary bar showing every input you just set:

New DOPE card page showing a summary bar with Zero 100yd, BC G7 0.326, Bullet 140gr ELD Match, MV 2710fps, Scope Ht 1.7 inches, Twist 1:8, Alt 1250ft, Temp 68F, RH 40%, Unit MOA, with no rows yet
Every input from the wizard, in one glance — before a single row exists.

Click Generate and GunCollector's ballistics engine computes velocity, energy, drop, time of flight, elevation correction, and wind hold at every distance:

Auto-generated DOPE card table with 10 rows from 100 to 1000 yards, showing velocity, energy, drop in inches, time of flight, elevation in MOA, and wind hold per mph of wind at each distance
100 to 1000 yards, computed in one click from data already sitting in your collection.

At 500 yards this load needs 9.85 MOA of elevation and 0.26 MOA per mph of wind. At 1000, it's 29.35 MOA and 0.60 MOA per mph — numbers you'd otherwise be pulling from a separate ballistics app and copying by hand. Every row is individually editable if you true the card against real impacts at the range, and clicking Generate again rebuilds the whole table from scratch if your inputs change.

Why this matters

The failure mode with DOPE cards isn't usually bad math — it's stale data. A card built once in a ballistics app and printed out doesn't know when you switch ammo lots or when your barrel picks up a few more rounds. Because this card is generated from the same rifle and ammo records you're already tracking, updating your load or your environment and hitting Generate again takes seconds, not a re-do from scratch.

Start tracking your rifles

Free during early access. No credit card required.

Create free account No credit card required