Partner API reference

The Partner API exposes the hosted pro solver behind the Strelok desktop apps. All endpoints accept a JSON body via HTTPS POST and return JSON. The base URL is https://api.strelokpro.com.

Access is by request. There is no self-serve signup; see Getting a key or request access.

Requests must be sent with Content-Type: application/json. All three endpoints share one set of base solve fields, listed under Common request fields below; each endpoint adds a few fields of its own.

Every request is authenticated with your partner API key, a secret that starts with sk_strelok_. Pass it in the Authorization header:

Authorization: Bearer sk_strelok_YOUR_KEY

The X-Api-Key header is also accepted with the same key as its value, for clients that cannot set an Authorization header.

Default limits are 60 requests per minute and 5,000 requests per day, per key. Higher limits are available; contact us if your integration needs them.

When a limit is exceeded the API returns HTTP 429 with a retryAfter value in the response body, in seconds, and the same value in a standard Retry-After response header. Wait at least that long before retrying, and prefer exponential backoff on repeated 429s. The daily count resets at midnight UTC.

These fields describe the rifle, load, atmosphere and wind. They are shared by all three endpoints. Values outside the listed range are rejected with HTTP 400.

Required

Optional

Returns the full trajectory at each rangeStep, annotated with Mach number, supersonic, transonic or subsonic zone, gyroscopic stability (Miller Sg) and the first transonic and subsonic ranges.

Additional request fields

Example request

6.5 Creedmoor, 140 gr, G7 0.315, 100 yard zero, 10 mph full-value wind:

curl https://api.strelokpro.com/api/partner/v1/solve \
  -H "Authorization: Bearer sk_strelok_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "muzzleVelocity": 2710,
    "ballisticCoefficient": 0.315,
    "dragModel": "G7",
    "bulletWeight": 140,
    "sightHeight": 1.8,
    "zeroRange": 100,
    "maxRange": 1200,
    "rangeStep": 100,
    "temperature": 59,
    "pressure": 29.92,
    "windSpeed": 10,
    "windDirection": 90,
    "includeSpinDrift": true,
    "twistRate": 8,
    "bulletDiameter": 0.264,
    "bulletLength": 1.427
  }'

Example response (abridged)

{
  "trajectory": [
    { "range": 100.2, "velocity": 2565.2, "time": 0.114, "energy": 2045.2,
      "dropInches": 0.0, "dropMOA": 0.0, "dropMil": 0.0,
      "windDriftInches": 0.61, "windDriftMOA": 0.58, "windDriftMil": 0.17,
      "path": -0.0, "mach": 2.298, "bcUsed": 0.315, "zone": "supersonic" },
    { "range": 200.3, "velocity": 2424.1, "time": 0.2345, "energy": 1826.4,
      "dropInches": 3.51, "dropMOA": 1.67, "dropMil": 0.49,
      "windDriftInches": 2.49, "windDriftMOA": 1.19, "windDriftMil": 0.34,
      "path": -3.51, "mach": 2.171, "bcUsed": 0.315, "zone": "supersonic" },
    { "range": 1200.1, "velocity": 1242.6, "time": 1.9625, "energy": 479.9,
      "dropInches": 534.37, "dropMOA": 42.53, "dropMil": 12.37,
      "windDriftInches": 123.19, "windDriftMOA": 9.8, "windDriftMil": 2.85,
      "path": -534.37, "mach": 1.113, "bcUsed": 0.315, "zone": "transonic" }
  ],
  "stability": { "sg": 1.51, "rating": "stable" },
  "transonicRangeYards": 1200.1,
  "subsonicRangeYards": null
}

Trajectory row fields: range (yards), velocity (fps), time (seconds), energy (ft-lb), dropInches, dropMOA, dropMil, windDriftInches, windDriftMOA, windDriftMil, path (inches relative to the sight line), mach, bcUsed, and zone (supersonic, transonic or subsonic). The stability rating is stable at Sg 1.5 or above, marginal from 1.0 to 1.5, and unstable below 1.0. transonicRangeYards and subsonicRangeYards are the first ranges where the bullet enters each zone, or null if it never does within maxRange.

Trajectory truing. Given the base solve fields plus drops you actually observed on target, the solver searches muzzle velocity (within plus or minus 200 fps) and optionally a BC scale factor (within plus or minus 15 percent) for the combination that best matches your observations, minimizing RMS error in MOA.

Additional request fields

Example request

curl https://api.strelokpro.com/api/partner/v1/true \
  -H "Authorization: Bearer sk_strelok_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "muzzleVelocity": 2710,
    "ballisticCoefficient": 0.315,
    "dragModel": "G7",
    "bulletWeight": 140,
    "sightHeight": 1.8,
    "zeroRange": 100,
    "maxRange": 1000,
    "rangeStep": 100,
    "twistRate": 8,
    "bulletDiameter": 0.264,
    "bulletLength": 1.427,
    "observations": [
      { "rangeYards": 300, "dropMOA": 4.5 },
      { "rangeYards": 600, "dropMOA": 14.3 },
      { "rangeYards": 900, "dropMOA": 27.6 }
    ]
  }'

Example response

{
  "muzzleVelocity": 2636.4,
  "bcScale": 1.0,
  "rmsErrorMOA": 0.059,
  "before": { "rmsErrorMOA": 1.132 }
}

muzzleVelocity is the trued velocity in fps, bcScale is the multiplier to apply to your BC (1.0 when trueBC is false), rmsErrorMOA is the residual error of the trued solution against your observations, and before.rmsErrorMOA is the error the untrued inputs produced. A request with an empty or missing observations array returns HTTP 400.

Hit probability by range for a rectangular target, given velocity, wind and aiming dispersion. Each run perturbs muzzle velocity, wind and optionally BC, resolves the trajectory, adds aiming error, and scores a hit if the impact falls inside the target box centered on the nominal aim point.

Additional request fields

Example request

curl https://api.strelokpro.com/api/partner/v1/montecarlo \
  -H "Authorization: Bearer sk_strelok_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "muzzleVelocity": 2710,
    "ballisticCoefficient": 0.315,
    "dragModel": "G7",
    "bulletWeight": 140,
    "sightHeight": 1.8,
    "zeroRange": 100,
    "maxRange": 1200,
    "rangeStep": 100,
    "windSpeed": 10,
    "windDirection": 90,
    "twistRate": 8,
    "bulletDiameter": 0.264,
    "bulletLength": 1.427,
    "runs": 400,
    "targetWidthInches": 18,
    "targetHeightInches": 24,
    "mvSD": 12,
    "windSD": 3,
    "aimErrorMOA": 0.5
  }'

Example response (abridged)

{
  "runs": 400,
  "byRange": [
    { "range": 100.2, "hitPct": 100.0, "meanDropInches": 0.0, "meanWindInches": 0.53 },
    { "range": 200.3, "hitPct": 100.0, "meanDropInches": 3.5, "meanWindInches": 2.17 },
    { "range": 1100.0, "hitPct": 22.5, "meanDropInches": 418.99, "meanWindInches": 87.14 },
    { "range": 1200.1, "hitPct": 20.2, "meanDropInches": 534.26, "meanWindInches": 107.84 }
  ],
  "maxEffectiveRange": 500.2
}

byRange has one entry per rangeStep with the hit percentage and the mean drop and wind drift in inches across all runs. maxEffectiveRange is the furthest range where the hit probability is at least 90 percent, or null if no range qualifies.

Errors are returned as JSON with an error message and a conventional HTTP status code.

Example error bodies

HTTP 400
{ "error": "muzzleVelocity is required" }

HTTP 401
{ "error": "Invalid API key." }

HTTP 403
{ "error": "API key revoked." }

HTTP 429
Retry-After: 60
{
  "error": "Rate limit exceeded",
  "message": "Rate limit exceeded (60 requests/minute).",
  "retryAfter": 60
}

Partner API keys are issued by contacting [email protected]. Include a short description of your integration and the request volume you expect. You can also reach us through the contact page.