GunSpec

All 39 single-call tools

Load carriage cost

  • gunspec_load_carriage
  • Builder
  • Read-only

Returns the metabolic energy a foot march costs carrying each of one to five firearms, with its magazines and attachments, on top of the other kit carried, by the US Army LCDA equation (Looney et al. 2022) or the Pandolf equation (1977). Use this tool when the question is how much harder one firearm is to carry than another over a distance. Masses come from the catalog; a firearm missing its empty or loaded weight comes back with an error instead of a cost. The answer is energy cost only: it does not predict fatigue, marksmanship or time to exhaustion.

Example usage

  1. 1

    A person asks

    • How much more energy does a 20 km march cost carrying an FN SCAR-L than an HK416, with seven magazines and 25 kg of kit?
  2. 2

    The assistant calls the tool

    tools/call
    json
    {  "name": "gunspec_load_carriage",  "arguments": {    "ids": [      "hk416",      "fn-scar-l"    ],    "magazines": 7,    "kit_kg": 25,    "distance_km": 20  }}
  3. 3

    The server answers

    Result
    json
    {  "model": {    "id": "lcda",    "name": "LCDA backpacking equation with the LCDA graded-walking term",    "equation": "M (W/kg body mass) = Mrest + (0.19 + η(1.78·S^0.58 + 0.27·S^4 + Mgrade)) · (1 + 1.96·L^1.36); Mgrade = 34·S·G·(1 − 1.05^(1 − 1.1^(100·G + 32))); S in m/s, G as rise/run, L = load ÷ body mass; Mrest from Cunningham (1991): (500 + 22·lean mas…",    "citations": [      {        "authors": "Looney DP, Lavoie EM, Vangala SV, Holden LD, Figueiredo PS, Friedl KE, et al.",        "year": 2022,        "title": "Modeling the Metabolic Costs of Heavy Military Backpacking",        "journal": "Medicine & Science in Sports & Exercise 54(4):646-654",        "doi": "10.1249/MSS.0000000000002833"      },      {        "authors": "Looney DP, Santee WR, Hansen EO, Bonventre PJ, Chalmers CR, Potter AW",        "year": 2019,        "title": "Estimating Energy Expenditure during Level, Uphill, and Downhill Walking",        "journal": "Medicine & Science in Sports & Exercise 51(9):1954-1960",        "doi": "10.1249/MSS.0000000000002002"      },      {        "authors": "Soule RG, Goldman RF",        "year": 1972,        "title": "Terrain coefficients for energy cost prediction",        "journal": "Journal of Applied Physiology 32(5):706-708",        "doi": "10.1152/jappl.1972.32.5.706"      }    ],    "validated": {      "speedMps": [        0.45,        1.97      ],      "loadFraction": [        0,        0.66      ]    }  },  "march": {    "bodyMassKg": 80,    "bodyFatPct": 15,    "kitKg": 25,    "magazines": 7,    "speedKmh": 4.8,    "speedMps": 1.333,    "gradePct": 0,    "terrain": "paved",    "terrainFactor": 1,    "distanceKm": 20,    "durationS": 15000,    "defaulted": [      "body_mass_kg",      "body_fat_pct",      "speed_kmh"    ]  },  "attachments": [],  "results": [    {      "firearm": {        "id": "hk416",        "name": "HK416",        "magazineType": "detachable_box",        "magazineCapacity": 30      },      "load": {        "firearmEmptyG": 3020,        "loadedMagazineG": 400,        "magazines": 7,        "magazinesG": 2800,        "attachmentsG": 0,        "carriedG": 5820,        "totalLoadKg": 30.82,        "loadFraction": 0.385,        "sources": {          "firearmEmptyG": "catalogue",          "loadedMagazineG": "derived"        }      },      "cost": {        "watts": 483.2,        "wattsPerKg": 6.04,        "energyKj": 7248.2,        "energyKcal": 1732.4      },      "delta": null,      "warnings": [],      "error": null    },    {      "firearm": {        "id": "fn-scar-l",        "name": "FN SCAR-L",        "magazineType": "detachable_box",        "magazineCapacity": 30      },      "load": {        "firearmEmptyG": 3500,        "loadedMagazineG": 490,        "magazines": 7,        "magazinesG": 3430,        "attachmentsG": 0,        "carriedG": 6930,        "totalLoadKg": 31.93,        "loadFraction": 0.399,        "sources": {          "firearmEmptyG": "catalogue",          "loadedMagazineG": "derived"        }      },      "cost": {        "watts": 489.9,        "wattsPerKg": 6.12,        "energyKj": 7347.9,        "energyKcal": 1756.2      },      "delta": {        "carriedG": 1110,        "watts": 6.6,        "energyKj": 99.7,        "energyKcal": 23.8      },      "warnings": [],      "error": null    }  ]}

    Captured from the live API on Oct 22, 2026. Lists and long text are shortened for display.

Related references

Arguments

  • string[]required

    One to five firearm slugs.

    Sent as
    ?ids=
  • numberdefault80

    Body mass of the person marching, in kg.

    Range
    40 – 160
    Sent as
    ?body_mass_kg=
  • numberdefault15

    Body fat as a percentage of body mass.

    Range
    3 – 50
    Sent as
    ?body_fat_pct=
  • numberdefault0

    Everything else carried, in kg: armour, pack, water.

    Range
    0 – 120
    Sent as
    ?kit_kg=
  • integerdefault1

    Full magazines carried in total, the one in the firearm included. 0 carries it unloaded.

    Range
    0 – 20
    Sent as
    ?magazines=
  • string[]

    Up to ten attachment slugs, added to every firearm by their recorded weight.

    Sent as
    ?attachments=
  • numberdefault4.8

    Marching speed in km/h.

    Range
    1 – 10
    Sent as
    ?speed_kmh=
  • numberdefault0

    Slope as a percentage, rise over run; negative is downhill.

    Range
    -30 – 30
    Sent as
    ?grade_pct=
  • stringdefaultpaved

    The surface marched over.

    Accepts
    Sent as
    ?terrain=
  • numberdefault20

    March distance in km.

    Range
    0.1 – 200
    Sent as
    ?distance_km=
  • stringdefaultlcda

    The equation: lcda, or pandolf for comparison with older studies (level and uphill only).

    Accepts
    Sent as
    ?model=

Each argument is sent to GET /v1/firearms/load-carriage as the parameter shown, so the same request can be made to the API directly, with your key, if you want to shape what comes back.

json