Ballistic Energy

Arrow profile lab

Build measured profiles for each arrow setup, compare them against one scenario, and keep the full config portable as a single JSON.

Active scenario

282.8 fps

74.0 ft-lb · 0.523 slug-ft/s

Target margin

+9.0 ft-lb

Against the 65.0 ft-lb target

Required FPS

265.0 fps

416.7 gr / 27.00 g arrow

Required grains

325 gr

At 300 fps to hit the target

Comparison spread

282.8-282.8 fps

0.0 fps across 1 profile

Measured Profiles

Profile development

One tab per measured arrow build.

Measured let-off

Scenario

Decision setup

Shared inputs used to compare every profile.

Scenario let-off

Model Controls

FPS sensitivities

Only the fitted speed layer moves here.

Utilities

Mass converter and status

Quick grains / grams conversion and handoff to the active setup.

Status

Profiles auto-save locally. Use Export JSON when you want a portable snapshot.

Comparison

Scenario results by profile

Click any row to jump back to that measured profile tab.

ProfileMeasuredScenarioKEMomentumMargin
278.8 fps282.8 fps +4.0 fps74.0 ft-lb0.523+9.0 ft-lb

Estimated speed vs arrow weight

Scenario: 69.0 lb · 27.5 in · 75%

Arrow 1

Kinetic energy vs arrow weight

Target line stays fixed while each profile projects its own energy curve.

Arrow 1 65 ft-lb target
Field manual and equations Detailed notation, exact equations, and how the fitted speed layer works.

Exact ballistic equations

These equations do not depend on the fitted profile model. Once arrow mass and speed are known, the outputs below are exact.

Kinetic energy

KE = grains × fps2 450240

Velocity is squared, so modest speed gains can move KE more than intuition suggests.

Momentum

p = grains × fps 225400

Momentum scales linearly with both arrow mass and speed, which is why heavier builds stay competitive here.

Required speed

fpsrequired = √ ( target KE × 450240 grains )

For the current scenario arrow, that requirement is 265.0 fps.

Fitted speed model

Each profile is a measured anchor. The model begins at that measured chrono and then moves away from it with tunable sensitivities.

fpsestimate = fpsmeasured + Δdraw weight × (fps per lb) + Δdraw length × (fps per inch) - Δarrow grains / 5 × (fps lost per 5 grains) + Δlet-off bonus + bias trim
fps measured

The chrono reading stored inside the active measured profile.

Δdraw weight

Scenario draw weight minus the profile’s measured draw weight.

Δdraw length

Scenario draw length minus the profile’s measured draw length.

Δarrow grains

Scenario arrow mass minus the profile’s measured arrow mass.

Δlet-off bonus

85% is the baseline, 80% gets half the configured bonus, 75% gets the full bonus.

bias trim

A final manual nudge if later chrono sessions show the whole model should shift.

How to use the comparison view

The table answers which measured build projects best for the current scenario. The charts show how that answer changes as arrow mass moves across the sweep window.

  • Measured is the chrono anchor saved inside each tab.
  • Scenario is the shared comparison target applied to every profile.
  • Margin is scenario KE minus target KE. Positive means the build clears the goal.
  • Export JSON saves every profile, every scenario input, and every heuristic into one file.
  • Import JSON restores that exact state, which makes profile iteration portable.