AimScan

Load Development: Ladder Tests and Chronograph Data

Turn a range day of ladder testing into clear numbers.

The Ammo tab is built for reloaders and anyone testing factory ammunition. It keeps load data, chronograph velocities and paper groups together.

AimScan records and compares your data. It contains no load data and gives no reloading advice. Always use published data from the powder and bullet maker and start low.

Batches

A batch is a group of identical rounds. For each batch you can record:

  • Name, cartridge and firearm.
  • Bullet and bullet weight (grains, with grams shown), powder and charge.
  • Primer, brass and how many times the cases were fired.
  • Lengths in mm: COAL, CBTO and jump to the lands.
  • Number of rounds, date loaded and notes such as powder lot or annealing.

Use Duplicate to start a new batch from an existing one.

Ladder tests

Tap Set up ladder test to create a whole test at once:

  1. Give the test a name, for example ".308 N140 ladder Oct".
  2. Enter the components that stay the same.
  3. Choose what you vary: powder charge or seating depth (CBTO).
  4. Enter start value, step and number of steps, plus rounds per step.
  5. Tap Create batches. AimScan makes one batch per step, all grouped under the test name.

Recording velocities

Open a batch and tap Record velocities. Type each velocity, or tap Import from chronograph and choose a CSV file or paste a list. AimScan finds the velocity column, reads comma, semicolon and tab separated files, and detects whether values are in m/s or fps.

For each string you can note the date, location, temperature, chronograph distance from the muzzle and remarks such as cold bore.

Per batch you get:

  • Average, lowest and highest velocity.
  • SD (standard deviation, calculated like chronographs do, with n − 1).
  • ES (extreme spread, highest minus lowest).
  • Muzzle energy in joules from the bullet weight.

Switch between m/s and fps at the top at any time.

Linking groups on paper

When you shoot a target with a batch, pick it under Ammo batch in the session details. The batch then shows the groups shot with it, with mean radius and extreme spread, next to the velocity data.

Comparing a test

AimScan powder charge ladder comparison with average velocity per charge

Tap Compare on a test to see all batches side by side:

  • A chart of average velocity per charge or seating depth, with bars for ±1 SD.
  • For charge ladders, a yellow section marks the flattest part of the ladder, where velocity rises least per grain. This is often a candidate velocity node. Confirm it with groups on paper.
  • A table with shots, average, SD, ES and MR per batch. The lowest SD and smallest group are shown in green.

As a rule of thumb, an SD under about 3 m/s (10 fps) and a small ES give less vertical spread at long range.