{
  "barrel_materials": [
    {"id": "ST52.3", "name": "ST52.3", "description": "Standard seamless steel tube", "hardness_hrc_range": [15, 25]},
    {"id": "SAE1026", "name": "SAE 1026", "description": "Carbon steel", "hardness_hrc_range": [15, 22]},
    {"id": "AISI1045", "name": "AISI 1045", "description": "Medium carbon steel", "hardness_hrc_range": [20, 30]},
    {"id": "E355", "name": "E355", "description": "European standard seamless tube", "hardness_hrc_range": [15, 25]},
    {"id": "custom", "name": "Custom", "description": "Custom specification"}
  ],
  "barrel_treatments": [
    {"id": "honed", "name": "Honed", "surface_finish_ra_range": [0.2, 0.4]},
    {"id": "skived_burnished", "name": "Skived & Burnished", "surface_finish_ra_range": [0.1, 0.3]},
    {"id": "hard_chrome", "name": "Hard Chrome Plated", "surface_finish_ra_range": [0.1, 0.2]}
  ],
  "rod_materials": [
    {"id": "CK45", "name": "CK45", "description": "Carbon steel for induction hardening"},
    {"id": "42CrMo4", "name": "42CrMo4", "description": "Alloy steel, high strength"},
    {"id": "AISI4140", "name": "AISI 4140", "description": "Chromium-molybdenum steel"},
    {"id": "20MnV6", "name": "20MnV6", "description": "Micro-alloyed steel"},
    {"id": "custom", "name": "Custom", "description": "Custom specification"}
  ],
  "rod_treatments": [
    {"id": "hard_chrome", "name": "Hard Chrome", "thickness_um_range": [20, 30], "hardness_hrc_range": [55, 65]},
    {"id": "nickel_chrome", "name": "Nickel-Chrome", "thickness_um_range": [25, 50], "hardness_hrc_range": [58, 65]},
    {"id": "nitrided", "name": "Nitrided", "hardness_hrc_range": [60, 70]},
    {"id": "ceramic", "name": "Ceramic Coating", "hardness_hrc_range": [70, 80]},
    {"id": "QPQ", "name": "QPQ (Quench-Polish-Quench)", "hardness_hrc_range": [55, 65]}
  ],
  "piston_materials": [
    {"id": "GGG50", "name": "GGG50", "description": "Ductile iron"},
    {"id": "C45", "name": "C45", "description": "Carbon steel"},
    {"id": "aluminum", "name": "Aluminum", "description": "Lightweight option"},
    {"id": "bronze", "name": "Bronze", "description": "Good wear resistance"}
  ],
  "head_cap_materials": [
    {"id": "C45", "name": "C45", "description": "Carbon steel"},
    {"id": "GGG50", "name": "GGG50", "description": "Ductile iron"},
    {"id": "aluminum", "name": "Aluminum", "description": "Lightweight option"},
    {"id": "steel_forged", "name": "Forged Steel", "description": "High strength applications"}
  ]
}