Internal ballistics as an API
Send cartridge, bullet, powder and charge — get back pressure, muzzle velocity, burn rate and more. The same physics as the ApexLOAD PRO calculator, ready for your own tools.
What the API does
You send the IDs of a cartridge, bullet and powder plus either a powder charge in grains or a fill rate between 50 and 105 %. Optional values such as max. overall length, case length, case capacity, barrel length and bullet length override our defaults, in inches or millimetres.
You get back
- Peak pressure and percent of the maximum allowed pressure
- Muzzle velocity and muzzle energy
- Powder burn rate and fill rate
- Barrel time
- The safety standard used (C.I.P. or SAAMI) and the resolved charge
How it works
- 1
Get a PRO licence
The API is part of ApexLOAD PRO — no separate contract.
- 2
Create your key
In Settings → API you create a personal key. It is shown only once; regenerating it revokes the old one.
- 3
Load the catalogues
Fetch JSON lists of cartridges, bullets and powders with their IDs. Catalogue calls are free.
- 4
Call calculate
POST your load and receive the results as JSON within a second.
Sample request and response
curl -X POST https://apexload.pro/api/public/v1/calculate \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"cartridge_id": "CID_0042",
"bullet_id": "BID_13719",
"powder_id": "PID_0101",
"fill_rate_pct": 95,
"barrel_length": 24,
"safety_standard": "CIP"
}'{
"inputs_used": { "charge_gr": 40.75, "charge_source": "from_fill_rate", ... },
"results": {
"muzzle_velocity_fps": 2566,
"max_pressure_bar": 3402.7,
"powder_burn_pct": 96.9,
"fill_rate_pct": 95.0,
"barrel_time_ms": 1.18,
"pressure_pct_of_max": 82.0
},
"safety": { "status": "ok", "standard": "CIP" },
"usage": { "calculations_used_last_365_days": 215, "budget": 500 }
}Full field reference, error codes and more examples are in Settings → API after signing in.
Who it is for
App and tool developers
Add verified internal ballistics to range apps, load managers and chronograph tools.
Gunsmiths and ammunition makers
Check whole load plans in batch before you build or test them.
Shooting clubs and ranges
Power in-house tools and member services with consistent calculations.
Data power users
Run ladders and what-if series from Excel, Python, Make or Zapier.
Where you can use it
- Your own website or mobile app
- Spreadsheets and scripts
- Internal shop and workshop systems
- Chronograph and range data workflows
Limits and fair use
- Available with an active ApexLOAD PRO licence only
- Each calculation counts as 1 of the 500 yearly calculations in your licence
- Up to 60 calculations per minute and 1,000 per day
- Catalogue calls do not use your calculation budget
- Same safety rules as the calculator — loads above 115 % fill rate are blocked
Frequently asked questions
Do I need a separate subscription for the API?
No. The API is included in ApexLOAD PRO. Each API calculation uses one calculation from your yearly budget.
Can I send a fill rate instead of a charge?
Yes. Send exactly one of charge in grains or fill rate (50–105 %). The response tells you which charge was used.
Which safety standard is used?
You can choose C.I.P. or SAAMI. Without a choice we use your profile preference, otherwise SAAMI. If a cartridge only has the other standard, the response says so.
Can I use metric units?
Yes. Set the unit to mm and all lengths you send are read as millimetres.
What happens if I exceed the rate limit?
You receive HTTP 429 with a retry_after value telling you when to try again.
Are the results a substitute for published load data?
No. Like every simulation, results are estimates. Always start low and follow published data and safe reloading practice.
May I show API results on my own website or resell them?
You may show results in your own tools and websites if they are marked "Calculated with ApexLOAD PRO" with a link to apexload.pro. Reselling results or catalogue data needs a separate agreement. See the API Terms of Use.
Start building with ApexLOAD PRO
Create your key in Settings and run your first calculation in minutes.
Get your API key