Frequently Asked Questions

How DOPE Book measures groups and velocity, and how the Group Analyzer works

General

What happened to AmmoLots?

AmmoLots has been rebranded to DOPE Book. The app started as a way to track ammunition by lot number, but it has grown into a full shooting performance tracker — range sessions, ballistics data, steel games, and group analysis.

The name DOPE stands for Data On Previous Engagements, a term precision shooters use for the recorded data that helps them make accurate shots. That's exactly what this app does — helps you build and reference your DOPE book digitally.

All your data, sessions, and account are exactly the same. Only the name and domain have changed. Please update your bookmarks to dopebook.io.

Measurement methods

What is Group Size?

Group size (also called "extreme spread" or ES) is the distance between the centers of the two shots that are farthest apart in your group. This is the most common way shooters measure accuracy.

How to measure

Identify the two shot holes that are farthest apart from each other
Measure from the center of one hole to the center of the other
This center-to-center distance is your group size

Tip If measuring edge-to-edge, subtract one bullet diameter to get the center-to-center measurement.

What is Mean Radius?

Mean radius is the average distance from each shot to the center of the group. Unlike group size which only considers your two worst shots, mean radius uses information from every shot in the group, making it a more statistically meaningful measurement.

Why use mean radius?

Every shot contributes to the measurement, not just the two farthest apart
More consistent and repeatable than group size, especially with larger shot counts
Better represents your rifle's true precision
Less affected by one "flyer" that can dramatically increase group size

How to calculate mean radius

The easiest way is to use a smartphone app that can analyze a photo of your target - there are several available for iOS and Android. If calculating manually:

Find the group center: This is the average position of all shots. Draw a vertical and horizontal line, measure each shot's distance from each line, then average those distances to find the center point.
Measure distances: Measure from the group center to the center of each shot hole
Calculate the average: Add all the distances together and divide by the number of shots

Useful conversions

To estimate your 95% group radius from mean radius, multiply by 2.1. This tells you the radius that 95% of your shots will fall within.

What is Extreme Spread (ES)?

In the context of velocity measurements (from a chronograph), extreme spread is the difference between your fastest and slowest shots. Lower ES indicates more consistent ammunition.

How to calculate

ES = Highest FPS − Lowest FPS

Most chronographs calculate this automatically. A good handload typically aims for an ES under 20 fps, though this varies by cartridge and use case.

What is Standard Deviation (SD)?

Standard deviation measures how spread out your velocity readings are from the average. Like mean radius for groups, SD uses all your shots rather than just the extremes, making it a more reliable indicator of consistency.

Interpreting SD

SD	Reads as
Under 10	Excellent consistency
10–15	Good for most applications
15–20	Acceptable
Over 20	Room for improvement

Most chronographs calculate SD automatically. You typically need at least 10 shots for SD to be meaningful.

Group Analyzer

Why mark Point of Aim (POA)?

Marking the POA on each analyzed target lets the app combine multiple groups shot at the same distance into a single collective readout — group size, mean radius, and MOA computed as if every shot came from one big group. This is the standard precision-shooting workflow: shoot 5, let the barrel cool, shoot another 5, repeat until you have a 20-shot dataset spread across several pictures.

To make the math work, every contributing group must have a POA marked. The app aligns each group on its POA before stacking shots, so the combined cloud reflects both aim error and dispersion the way it would if you'd fired the whole string at one target.

If a group is missing its POA, it's excluded from the collective readout and you'll see a note showing how many groups were skipped. Groups analyzed before re-analyze support was added also can't contribute — delete and re-analyze them if you want them included.

Why are the numeric fields locked on analyzed groups?

Group size, mean radius, distance, and shot count come from the analyzed photo. The annotated image bakes those numbers in — editing them in the form would silently drift the displayed values away from the picture.

To change any of them, click Re-analyze. The analyzer reopens on the original photo with all your shots, POA, and calibration pre-loaded so you can adjust a misplaced marker, change distance, or re-mark shots. When you save, the annotated image regenerates to match.