Straighten the page
Corner markers recover the target's physical scale, even when the camera is not square to the paper.
Measure.
Correct.
Tackdriver reads a paper target from your iPhone, measures center to center, and turns offset into optic clicks.
Free on iPhone. Works offline. No ads, subscription, or account required to start.
One photo becomes a measured group.
The printed page gives the camera scale. Tackdriver corrects perspective before it measures the holes.
Measure the group
See center-to-center spread, mean radius, point of impact, and confidence in the units you use.
Turn the right clicks
Add your optic once. Tackdriver converts measured offset into the correct elevation and windage clicks.
Print the target you need.
Precision zero, red-dot zero, diagnostics, group tests, and load ladders print at exact scale from the app.
Each sheet carries its own scale and identity, so the photograph can be checked against the paper you actually shot.
Measure the zero before you trust the solver.
The target, rifle, load, atmosphere, and trajectory stay in one range record. Weak evidence gets a warning, not false precision.
- Group confidence
- Bounds show what the sample can support.
- Trajectory engine
- Three-degree-of-freedom point mass with RK4 integration.
- Long-range effects
- Spin drift, aerodynamic jump, Coriolis, and inclined shots.
- Velocity truing
- Back-solve muzzle velocity from measured drop.
Checked against published trajectories to 1,000 yards.
Continuous tests compare velocity, time of flight, drop, and wind drift. Drag functions include G1 through G8 and RA4.
The range still works when the signal does not.
Measurement, printing, ballistics, and the logbook work offline. Private records stay on your phone and can sync through your private iCloud database.
Read the privacy policyThe first questions
How does Tackdriver measure a rifle group from a photo?
Printed corner markers let the app correct perspective and recover the target's physical scale. It then measures the holes in the target's own coordinate system.
Does it work without cell service?
Yes. Target printing, scanning, group measurement, ballistics, and the local range logbook work offline. iCloud sync and public features wait for a connection.
Can it tell me how many scope clicks to turn?
Yes. Add the optic's adjustment value and direction, then Tackdriver converts measured point-of-impact offset into the correct number of clicks.
Is Tackdriver free?
Yes. Tackdriver has no subscription, no advertising, and no paywalled features.
Does Tackdriver upload full-resolution target photos?
Private scans stay in the private logbook and private iCloud database when sync is available. A public post includes a smaller copy only when you choose to share it.
Bring paper. Bring your phone.
Tackdriver for iPhone is free, offline-first, and preparing for App Store release.