Bofors gun emplacement and attached pillbox

This is a 40mm Bofors light anti-aircraft gun emplacement, with an attached pillbox, built in November and December 1940. It was designed by the Directorate of Fortifications and Works to defend the Royal Ordnance Factory in Chorley (identified as Vulnerable Point 426). The structure was built from fair-faced brick walls with concrete gun platforms, floors, and a roof.

The gun emplacement is circular and semi-sunken, approximately 4.57 metres in diameter. The concrete gun floor sits 0.6 metres below ground level and has a recessed gutter running around its circumference. A low brick retaining wall surrounds the emplacement, with four ammunition lockers set into the wall. A central, circular holdfast pedestal, 1.52 metres in diameter and 0.76 metres high, sits on the gun floor. This pedestal contains a square cable duct that rises vertically, and a square steel mounting frame with six projecting holdfast bolts is set into its upper surface. A circular, brick-lined predictor pit with a cable duct in its floor is positioned to the south-west of the emplacement.

Attached to the north-east side is a semi-sunken rectangular pillbox of Type 23 design. The emplacement and pillbox appear to have been constructed together. The pillbox is built to a ‘blast and splinter-proof’ specification, with walls 0.58 metres thick and a flat, 0.3 metre thick, reinforced concrete roof. Three walls are pierced by narrow, splayed rifle embrasures. Behind the pillbox, an open forecourt served as a weapons pit for a pintle-mounted Lewis anti-aircraft light machine gun and was accessed through a gap in the western corner wall; the walls of this weapons pit have subsequently been reduced in height to be flush with the surrounding ground level.

The pillbox interior contains a single square room with fair-faced brick walls, a concrete floor, and a central brick anti-ricochet wall. Access is via steps descending from the weapons pit through a low doorway in the pillbox's western corner.