Load Development Plotter
A browser-based load-development notebook for ladder tests, OCW, Satterlee velocity ladders, and group-plus-SD analysis.
Use this after the range trip. Enter the charges you tested, the velocities or groups you recorded, and let the tool show you whether there is a real pattern in the data or just a tempting little mirage.
Where are you in the process?
Three doors in. The first one teaches as it goes. The second one assumes you already know what you shot. The third one picks up a test you started earlier.
What load development actually is.
You don't need to read this if you've done it before. If you haven't: four cards, two minutes, then we'll help you pick a method.
Finding the powder charge that shoots best in your rifle.
Two identical rifles, identical ammo, identical optics will often prefer different powder charges by a few tenths of a grain. Load development is the structured search for the one yours likes.
The same load that's tight in your buddy's rifle may be mediocre in yours.
Barrel harmonics, chamber dimensions, throat erosion, and a dozen other variables make every rifle its own instrument. A load worked up for one is a starting point for another, not an answer.
Shoot a structured test. Enter the data here. Read the result.
You'll load a range of charge weights, shoot them in a specific order, record what each one did, and this tool will tell you whether a pattern is there - or whether you need more shots to know.
Start at the published starting load. Watch for pressure signs.
This tool documents what your tests showed. It does not replace your reloading manual. Sticky bolt, ejector marks, cratered primers, case-head expansion - if you see any of them, stop.
Which test should you run?
Three questions. We pick a methodology that fits your gear, your range, and how many rounds you want to spend. You can override the recommendation at any point.
Do you have a chronograph?
How far can you shoot?
How many rounds are you willing to shoot?
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All four methods.
Each has trade-offs. Pick the one that matches the constraints you actually have, not the one that sounds most impressive.
Pre-flight checklist.
The hardest part of a test isn't the math. It's not making a labelling mistake at the bench, and not getting your shots out of order at the range. Walk this list before you go.
About your rifle and load.
Most of these fields are optional but they make your test record useful later. If you run a similar test next year, having the conditions logged tells you whether the change you're seeing is your load or your weather.
Conditions (optional)
Type in what you shot.
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Your test library.
Everything is stored locally on this device. Clearing your browser data will erase these records. Export anything you want to keep.
NOT A SUBSTITUTE FOR YOUR RELOADING MANUAL
This tool helps you analyze data from tests you have already shot. It does not provide load data, recommend charge weights, or replace the safety guidance in published reloading manuals. Always start at the published starting load. Always watch for pressure signs - sticky bolt, ejector marks, cratered primers, case-head expansion.
The author of this tool is not responsible for loads you choose to develop or shoot. Reload at your own risk.
Glossary
About this tool
The Load Development Plotter is a Holdover utility for handloaders. It does node detection on data you collected yourself, in your rifle, on your range. It teaches the four common methodologies as you use them. Everything runs in your browser. Your test records never leave this device.
A note on honesty: the methods this tool implements - particularly Satterlee - have been usefully criticised in recent years for producing false positives at small sample sizes. The tool surfaces confidence assessments alongside every result for that reason. A flat spot in 10 rounds is a hypothesis. Twenty more rounds will tell you if it's real.
What The Load Development Plotter Helps You See
The Load Development Plotter is a browser notebook for data you already collected at the range. Enter charge labels, velocities, group notes, or point-of-impact observations, then compare whether the pattern looks repeatable enough to investigate further.
It is designed for organization and analysis: ladder notes, OCW-style comparisons, Satterlee velocity ladders, and group-plus-standard-deviation records. The tool helps keep evidence in one place while leaving load-data decisions where they belong: current manuals, component data, and cautious range confirmation.
Quick FAQ
Does the Load Development Plotter provide load data?
No. It analyzes data you already collected from published-data-based tests. It does not recommend charge weights or replace a current reloading manual.
Which test types can it organize?
It supports ladder tests, OCW-style notes, Satterlee velocity ladders, and group-plus-standard-deviation records.
Where are my saved tests stored?
Saved tests stay locally in your browser on the same device unless you export or print the result yourself.
What should I do if the data looks inconclusive?
Treat inconclusive output as inconclusive. The tool is meant to reveal patterns, not force a decision from weak data.
Cite This Tool
Suggested citation: Holdover, "Load Development Plotter", last updated May 19, 2026, https://www.holdover.ca/load-development-plotter/.
Safety Note
This tool does not provide load data, recommend a charge weight, or replace a published reloading manual. Start from published data, work carefully, and stop if you see pressure signs.
Sources
- SAAMI, Frequently Asked Questions, accessed May 17, 2026.
- SAAMI, Recommendations for Safe Ammunition Storage and Handling, accessed May 17, 2026.
- Hodgdon Powder Company, General Warnings, Rev. May 15, 2023, accessed May 17, 2026.
- Hornady, 12th Edition Hornady Handbook of Cartridge Reloading, accessed May 17, 2026.
Related Holdover Tools
If this is the job on your bench, these nearby tools are usually part of the same workflow.