| Year | 1916 |
| Weapon Type | Heavy Howitzer |
| Origin & Designer | Britain/Vickers |
| Numbers Produced | 14 (Mk. II) 43 (Mk. IV) |
| Crew | [@crew] |
| Calibre | 304.8mm (L/17.3) |
| Elevation | [@elevation] |
| Traverse | 15° Left & Right |
| Breech | Asbury Interrupted Screw |
| Recoil | Hydropneumatic |
| Gun Sight | [@gun_sight] |
| Gun Mount | [@gun_mounts] |
| Carriage | Siege Carriage |
| Trailers | [@trailers] |
| Gun Shield | [@gun_shield] |
| Armoured Plate | [@armoured_plate] |
| Barrel Length | 5.650mm (Mk. II) 5.257m (Mk. IV) |
| Overall Length | [@length] |
| Width | [@width] |
| Height | [@height] |
| Weight | [@weight] |
| Round Weight | 750 kg (Bagged Charge) |
| Muzzle Velocity | 447 m/s |
| Feed | [@feed] |
| Magazine Capacity | [@magazine_capacity] |
| Practical Rate of Fire | [@practical_rate_of_fire] |
| Rate of Fire | [@rate_of_fire] |
| Maximum Rate of Fire | [@maximum_rate_of_fire] |
| Maximum Ceiling | [@maximum_ceiling] |
| Maximum Ground Range | [@maximum_ground_range] |
| Maximum Range | 10.000m (Mk. II) 13.000 (Mk. IV) |
| Armour Penetration | [@armour_penetration] |
| Traction | Motorized (Six Loads) |
| Variants | [@variants] |
| Notes | The BL 12in was a larger version of the BL 9in howitzer and saw action in World War One. It was a static weapon which had to be dismantled into six loads for towing. Some remained in use in 1940 with four being left in France by the BEF and the remainder used for home defence. |
