BL 7.2 inch Howitzer Mk.I

BL 7.2-inch howitzer Mk I-IV
7.2-inch howitzer of 51st Heavy Regiment, Royal Artillery, France, 2 September 1944. Gun crew emplacing recoil ramps in rear and setting wheel brakes. Front ramps prevent howitzer from rolling past position fired from.
Type	Howitzer
Place of origin	United Kingdom
Specifications
Weight	22,000 lb (10,000 kg)
Length	24 ft 4 in (7.42 m)
Barrel length	22.4 calibres / 14 ft 3 in (4.34 m)
Width	9 ft (2.7 m)
Height	4 ft 3 in (1.30 m)
Crew	10
Shell	HE
Shell weight	202 pounds (92 kg)
Calibre	7.2 inches (182.9 mm)
Breech	Welin screw & Asbury mech
Carriage	Box trail
Elevation	0° to 45°
Traverse	4° Left & Right
Rate of fire	1/3 rpm
Muzzle velocity	1,697 ft/s (517 m/s)
Maximum firing range	16,900 yd (15,500 m)

The BL 7.2-inch howitzer Mks I–V and Mk 6, were a series of heavy artillery pieces used by the British Army throughout World War II.

In 1940 the British Army concluded that the only available heavy artillery, the World War I era BL 8-inch howitzer, had insufficient range for the conditions of World War II. As a stopgap the decision was made to re-line the existing barrels to a smaller calibre and develop a new range of ammunition to achieve the desired ranges.

The 8 inch barrels were re-lined to 7.2 inches (180 mm) and the old carriages were retained although the original steel rimmed wheels were replaced with new pneumatic balloon-tyre wheels, as was consistent with the motorisation of the British Army. The new four-charge ammunition increased the range to 16,900 yd (15,500 m), but when fired at full charge the recoil caused the weapon to rear violently and jump backwards. To help counter this, two wedge shaped ramps were placed behind the wheels although the gun could sometimes still jump over them, presenting a hazard to crews. Marks I–IV differed only in the original 8-inch barrel used and the type of conversion; some barrels and carriages were also supplied from US World War I stocks.

In 1944 several 7.2-inch barrels were placed in the US Carriage M1 used by the 155 mm Long Tom already in use by the British Army, becoming the BL 7.2-inch howitzer Mk V. Few Mk Vs were produced and it was never issued to batteries, as it was apparent that the Carriage M1 was capable of accepting greater recoil forces.

The BL 7.2-inch howitzer Mk 6 (there was a shift from Roman numerals) retained the Carriage M1 of the Mk V but had a new built 7.2 inch barrel 6 ft 5 in (1.96 m) longer than previous marks and a fifth charge was added to the ammunition. The longer barrel and extra charge provided a range increase to 19,667 yd (17,984 m). The new carriage also provided a far more stable platform, greatly increasing accuracy. The Mk 6 was considered a highly effective gun.

The original marks performed well. The first 7.2-inch howitzers were issued to batteries from mid-1942 and used in action in North Africa and later following the Normandy landings. In Burma they were provided as a pool of two guns per corps and used by Regiments as required. By the end of 1944, most of the earlier marks had been replaced by the Mk 6.