The Bofors Gun – Part V: More on the Breda Mountings

Increased rate of fire
The increased rate of fire has been achieved by reducing the recoil stroke by more than 50% from 9.84 to 3.94 in (250 to 100 mm) and by speeding the cycle of breech unlocking, spent case extraction, fresh round loading and breech locking. The dual-feed arrangement retains the symmetrical but separate magazine system of the Twin 40L70 Compact, but adds separate 100-round magazines for each ordnance beside the elevating mass. This latter arrangement meant a revision of the turret’s forward contours to accommodate the magazines supported by the trunnion walls to feed APFSDS rounds, via a chain mechanism, to the two-row fan-shaped shifter. This is a boosted unit, and its upper row handles the APFSDS ammunition from the upper magazine while the lower row deals with the rounds (generally PFHE) from the main magazine.

The tactical thinking behind the Twin Fast Forty is that aircraft or missiles can be engaged from 3,280 down to about 1,095 yards (3000 down to about 1000 m) with the standard PFHE ammunition, and that any ‘leakers’ can then be engaged in a last-ditch defence from 1,095 to 110 yards (1000 down to 100 m) by an instantaneous switch to the devastating APFSDS ammunition. The PFHE projectile is already a potent type, with fragments hitting the target with a relative velocity of 6,562 ft (2000 m) per second. The 7.55-lb (2.3-kg) APFSDS round is designed to ensure total destruction of missile targets at short range by detonating their warheads. The projectile leaves the muzzle at 4,429 ft (1350 m), the sections of the sabot then falling away to leave the sub-calibre penetrator, which weighs 12.35 oz (350 g) and has a diameter of only 0.59 in (15 mm), to fly into the target and explode its warhead.

The Twin Fast Forty is produced in the same variants as the Twin 40L70 Compact, namely the Twin Fast Forty Tipo A with a main ammunition capacity of 736 rounds in seven horizontal rows and the Twin Fast Forty Tipo B with a main ammunition capacity of 444 rounds in four horizontal layers. Both types have the same 200-round stowage for APFSDS rounds, but can be installed with the main magazine above or below deck, the former by use of a barbette to support the mounting. The barbette is fitted with access doors for ammunition loading.

Simpler and cheaper
Breda also produces a less sophisticated range of mountings for twin and single 40-mm guns. Used only by the West German navy was the Breda Twin 40L70 Tipo 106 twin gun mounting. This was a powered mounting designed for local powered or manual control with a NIFE SRS-5 reflector or Mirasole line-of-sight aiming system or, for optimum results, remote control. The mounting weighed 14,572 lb (6610 kg) with unloaded magazines, and the ammunition supply comprised 64 rounds in two 32-round overhead magazines, though four-round clips could also be fed manually into the automatic feeder. The mounting traverses and the ordnances elevate, both at the maximum rate of 95° per second, with an acceleration of 125° per second².

More widely used is the Twin 40L70 Tipo 64 twin mounting, which is a more sophisticated and capable mounting than the Tipo 106, and provided with special barrel-cooling arrangements. The Tipo 64 is again a powered mounting designed for local powered or manual control, with a NIFE SRS-5 reflector, Mirasole line-of-sight or simple graticule aiming system or, for best results, remote control. The mounting weighs 17,747 lb (8050 kg) with unloaded magazines, and the ammunition supply comprises 200 rounds in two 100-round overhead magazines, though four-round clips can also be fed manually into the automatic feeder, which also incorporates a fuse-setting sub-system. The mounting traverses at the minimum rate of 85° per second with a minimum acceleration of 110° per second², and the ordnances elevate at the minimum rate of 95° per second with a minimum acceleration of 125° per second².

Breda has also produced two important light mountings for the 40-mm Bofors, and these mountings are in very widespread service. The 40L70 Tipo 107 single mounting can be regarded as the counterpart to the Tipo 106 twin mounting. It is a powered mounting designed for local powered or manual control, with a NIFE SRS-5 reflector or Mirasole line-of-sight aiming system or, for best results, remote control. The mounting weighs 8,179 lb (3710 kg) with its magazine unloaded, and the ammunition supply comprises 32 rounds in an overhead magazines, though four-round clips can also be fed manually into the automatic feeder. The mounting traverses and the ordnance elevates, both at the maximum rate of 95° per second, with an acceleration of 125° per second². The 40L70 Tipo 564 single mounting can be regarded as the counterpart to the Tipo 64 twin mounting, and generally has a crew of three comprising gunner, loader and off-mounting ammunition replenishment number, though there is a version for operation by a single man only. The Tipo 564 is a powered mounting designed for local powered or manual control, with a NIFE SRS-5 reflector, Mirasole line-of-sight or simple graticule aiming system or, for best results, remote control. The mounting weighs 7,496 lb (3400 kg) with its magazine unloaded, and the ammunition supply comprises 144 rounds in an extremely compact overhead magazine, though yet again four-round clips can also be fed manually into the automatic feeder. The mounting traverses at the rate of 80° per second with an acceleration of 120° per second², and the ordnance elevates at the rate of 45° per second with an acceleration of 130° per second². The Tipo 564 is also designated as the Breda/Bofors 350P.

The Spanish navy uses a licence-built version of the Bofors-Breda single mounting for the 40L70 weapon. Produced by Bazan, this equipment is designated the Bofors-Breda 144 Modello 76. The mounting weighs 7,275 lb (3300 kg), and can be traversed through 360° at the rate of 85° per second. The ordnance can be elevated in an arc between -10° and +85° at the rate of 45° per second.

Land-based derivative
The Twin 40-mm Field Mounting is a 40-mm twin mounting developed as a land equipment from the Twin 40L70 Compact naval installation, and is designed for fully automatic operation without any onboard crew but using an external power source and control from a radar fire-control system. Like its naval counterpart, the Field Mounting offers very considerable fire power to a tactically significant range, and the dedicated linkage of a number of such equipments with a radar-directed fire-control system offers the very real probability of stand-off destruction of aircraft attacking high-value sites such as airfields, harbours, industrial installations, command centres and communications chokepoints.

The system is based on a lightweight platform carried on a two-axle carriage, and towed to any suitable 6×6 truck. In firing position the carriage is stabilised, with its wheels off the ground, by an arrangement of six jacks: one at each end of the carriage, and two at the ends of short outriggers on each side. The carriage accommodates the system’s magazine. The platform is designed to provide the mounting with 360° traverse, carries the aluminium alloy trunnion supports and the two closely located guns. It also supports the ammunition and servo motors, the upper ammunition feed mechanism and the firing mechanism. All this is enclosed in a fully watertight cupola of reinforced fibreglass and is fitted with three access hatches. The mounting is electrically controlled, and the traverse and elevation rates are moderately high for a system with so great a moving mass. These are traverse 90° per second with an acceleration of 120° per second², increased in later models to 100° per second with an acceleration of 150° per second²; and elevation 60° per second with an acceleration of 120° per second², increased in later models to 150° per second². These allow even faster-crossing targets to be engaged at close ranges.

The circular magazine on the carriage holds 444 rounds, which are loaded from four-round clips via a hatch on each side of the carriage into four horizontal layers with a transport system to shift the rounds towards an ammunition hoist on each side. Thus there is a separate feed/hoist mechanism for each barrel, which ensures that the system can continue to function in part even if one barrel is out of action. The action of the ammunition system is entirely automatic, and lifts rounds out of the magazine at the rate of four every 0.7 second.

The two guns are Breda-modified 40L70 weapons, each with a cyclic rate of 300 rounds per minute, and these use the standard range of ammunition for this important gun.

The Field Mounting used with the Hollandse Signaalapparaten (now Thales Nederland) Flycatcher fire-control system to produce the Breda/HSA Guardian point-defence system, which in typical form comprises one Flycatcher fire-control system and two or three Field Mountings.

Flycatcher fire-control system
Properly designated the HSA VL4/41, Flycatcher is designed for the detection, identification, tracking and engagement of medium-, low- and very low-level attack aircraft with guns and/or SAMs. It is thus a highly versatile system, and uses a radar derived from that used in the Dutch army’s 5PFZ CAl Caesar version of the multi-national 5PFZ self-propelled AA cannon system. The Flycatcher system weighs about 4,409 lb (2000 kg) and is accommodated in a container 8 ft 11.5 in (2.73 m) long, 9 ft 11.5 in (2.12 m) wide and 7 ft 0 in (2.13 m) high increasing to 11 ft 11.75 in (3.65 m) high with the dual search-and-track antenna system raised. The pulse-Doppler radar system operates I-band for the detection of targets out to a 360° range of some 21,875 yards (20000 m). Possible targets are interrogated by the system’s integral IFF sub-system, and tracked in the I/K-bands with data displayed on the operator’s north-oriented plan position indicator screen. The operator designates a target, which is then acquired and tracked automatically as the digital system solves the fire-control problem and lays the relevant weapon on to the right bearing and elevation.

The system is capable of engaging targets moving at up to Mach 2 with vertical speeds of up to 985 ft (300 m) per second, the associated weapon opening fire as soon as the right engagement criteria have been established. The system also possesses a TV camera boresighted to the radar, allowing a useful passive back-up tracking capability should the radar have to be shut down for fear of anti-radiation missiles. The radar has extensive ECCM capabilities, and other anti-interference features.

The mounting is also offered with a version of a French naval optronic director system, the CSEE (later CS Défense then Matra Défense then Matra Systèmes & Information, later EADS Systems & Defence Electronics and now Sagem Défense Sécurité) Naja. This gyro-stabilised unit weighs some 1,102 lb (500 kg) and is capable of 360° traverse and elevation in an arc between -25° and +75° each at the rate of 60° per second. The main assemblies are an optical sight system giving x2.5 magnification with 19° field of vision or x8 magnification with 6° field of vision, a daylight or low-light-level TV camera, a laser rangefinder and an analog computer.

Specification

Breda Twin 40L70 Compact naval 40-mm twin AA gun mounting

Type: naval twin point defence tactical AA gun mount

Calibre: 40 mm

Barrel length: 70 calibres

Mounting: powered turntable with fibreglass turret

Weights: (Tipo A) 12,346 lb (5600 kg) without ammunition and 16,314 lb (7400 kg) with ammunition, and (Tipo B) 11,905 lb (5400 kg) without ammunition and 14,330 lb (6500 kg) with ammunition

Dimensions: swept radius 9 ft 6.25 in (2.902 m); length 15 ft 1.25 in (4.602 m); width 10 ft 6 in (3.20 m); height, above-deck assembly 7 ft 10.5 in (2.40 m) and under-deck assembly 4 ft 4 in (1.32 m) for Tipo A and 3 ft 0.25 in (0.92 m) for Tipo B

Traverse/elevation: 360°/-13° to + 85°

Rate of fire (per barrel): 300 rounds per minute (cyclic)

Horizontal range: 13,670 yards (12500 m) maximum

Slant range: 3,830 to 4,375 yards (3500 to 4000 m) effective depending on target size and aspect

Crew: 0

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