QF Mark VII (40 mm)

The 40 mm QF Mark VII on HMS Armada.

Description

The 40 mm QF Mark VII is a naval anti-aircraft single mounting that consists of a British-produced Bofors 40 mm L/60 gun. The Bofors 40 mm L/60, also known as the "Bofors L/60", the "Bofors gun", or simply "the Bofors", was a highly successful Swedish anti-aircraft gun design of the interwar period and was widely used during the Second World War by both sides and in all theatres and remained in service long after the end of WWII.

General info

The QF Mark VII has a barrel diameter of 40 mm and has a barrel length of 2.25 m. It has a magazine size of 4 rounds and has a rate of fire of 160 rounds per minute, though firing for too long will jam the gun.

Available ammunition

There are three ammunition choices available:

• Universal: AP-T · HEFI-T
• 40 mm HE clips: HEFI-T · HEFI-T · HEFI-T · AP-T
• 40 mm AP clips: AP-T · AP-T · AP-T · HEFI-T

Penetration statistics
Ammunition	Penetration @ 0° Angle of Attack (mm)
	10 m	100 m	500 m	1,000 m	1,500 m	2,000 m
HEFI-T	3	3	3	3	3	3
AP-T	81	78	68	58	49	41

Shell details
Ammunition	Velocity (m/s)	Projectile mass (kg)	Fuse delay (m)	Fuse sensitivity (mm)	Explosive mass (TNT equivalent) (g)	Ricochet
						0%	50%	100%
HEFI-T	874	0.9	0	0.1	67.13	79°	80°	81°
AP-T	874	0.89	-	-	-	47°	60°	65°

Comparison with analogues

All naval Bofors 40 mm L60 guns are virtually identical, the only difference between them being the rate of fire: all single mounts fire at 160 rpm, while twin and quadruple mounts fire at 156 rpm. They all fire the same ammunition from 4-round ammunition clips and have a short enough reload that they can sustain continuous fire as if there wasn't a reload at all. In other words, their cyclic rate of fire (mechanical rate of fire) is the same as their effective rate of fire (rate of fire with reload times taken into account). All naval Bofors 40 mm L60 guns can jam if fired for too long.

The naval Bofors 40 mm L/70 is, by and large, superior with a much higher rate of fire of 240 rounds per minute. Other differences include the HE round, with >115 g TNT eq., higher muzzle velocity (>1000 m/s), and the exchange of the L/60's AP-T shells for a potent HE-VT option.

Compared to other common guns of similar calibre:

• 3.7 cm SK C/30 (37 mm): The 3.7 cm SK C/30 has a higher muzzle velocity for both its AP and HE rounds (1,000 m/s) and has a stronger AP round (87 mm @ 10 m, 0°; 0.0374 kg TNT equivalence); but it has a much slower rate of fire (30 rpm), has a weaker HE round (27.4 g TNT equivalence), and has a lower projectile mass for both its AP round (0.82 kg) and HE round (0.75 kg). This gun is single-shot and cannot jam.

• 3.7 cm FlaK-Lafette C/36 (37 mm) and 3.7 cm FlaK-Lafette LM/42 (37 mm): These guns have a higher rate of fire (250 rpm); but they have a lower muzzle velocity for both their AP round (815 m/s) and HE round (845 m/s), have a weaker AP round (67 mm @ 10 m, 0°) and a weaker HE round (44.03 g TNT equivalent), and have a lower projectile mass for both their AP round (0.7 kg) and HE round (0.62 kg). These guns fire from a 5-round ammunition clip and have a very quick reload, so their cyclic rate of fire and effective rate of fire are practically identical. They cannot jam.

• 37 mm/67 70-K (37 mm): The 70-K has a lower rate of fire (150 rpm), has a weaker AP round (79 mm @ 10 m, 0°) and a weaker HE round (56.98 g TNT equivalence), and has a lower projectile mass in both its AP round (0.76 kg) and HE round (0.72 kg), but has a slightly higher muzzle velocity for both rounds (880 m/s). It fires from a 500-round magazine and can jam if fired for too long.

• 2pdr QF Mk.IIc (40 mm) and 2pdr QF Mk.VIII (40 mm): These guns have a higher rate of fire (200 rpm), but they have a lower muzzle velocity for its AP and HE rounds (701 m/s), have a weaker AP round (60 mm @ 10 m, 0°) and a weaker HE round (71 g TNT equivalence), and have a lower projectile mass in both their HE (0.72 kg) and AP (0.76 kg) rounds. They fire from a 56 round magazine and cannot jam.

Usage in battles

One of the best medium-range anti-aircraft cannons in the game, the QF Mark VII provides very good AA coverage for any ships that it's mounted on. With a 0.0986 kg TNT equivalent explosive charge in each HE round, any hit on an enemy aircraft will usually result in critical damage, if not a kill. The rounds that this gun fires have an above-average muzzle velocity and projectile mass, resulting in a much further effective range than guns of a similar calibre: laterally (i.e. targeting surface targets), the maximum range is about 3.25 km. This is most prevalent on patrol boats and other smaller vessels because it allows those equipped with the QF Mark VII to knock out enemies safely outside the maximum range of almost every other autocannon (most notably, the German 2 cm/65 C/38, which have a maximum range of roughly 2 km).

Despite the gun's small magazine size of only four rounds, the reload is short enough that there isn't any noticeable difference between its cyclic rate of fire (the rate of fire only considering the mechanical speed of the gun) and its effective rate of fire (the rate of fire accounting for reload times). In other words, it can sustain virtually continuous fire, as if there was no reloading at all. However, this comes at the cost that if fired for too long, the gun can jam. For this reason, it can be advantageous to set the AI gunners to only target aircraft. If allowed to target surface targets, the AI gunners will often waste ammunition on targets well outside of the gun's maximum range, leaving the guns jammed when actually needed.

The main ammunition choice to take should be 40 mm HE clips since it contains the highest ratio of HE to AP rounds. On patrol boats and other smaller vessels though, a small amount of 40 mm AP clips should also be taken to deal with any armoured targets that may come up. With a maximum penetration of 80 mm, the AP rounds trivialize most armour that they come across. AP can also be used when an enemy is approaching straight on, in which case an already destroyed bow compartment will tank most HE damage; the AP rounds can pass through and deal damage to the rear of the boat. On destroyers though, there is no reason at all to take the AP clips. While the AP rounds do have a very gun penetration for its calibre, armoured targets are more effectively dealt with using the destroyer's main armament anyway. With the 40 mm HE clips, the QF Mark VII will have the highest effectiveness against its intended targets, aircraft and small boats.

Pros and cons

Pros:

• Large explosive mass in HE round
• High-penetration AP round
• Very quick reload

Cons:

• Can jam if fired for too long

History

In 1928, the Swedish Royal Navy contracted the Bofors Company to design a suitable replacement for their Vickers 2-pounder guns anti-aircraft guns (the Vickers "Pom-Poms"). Work on the design began right away and a prototype model was produced by mid-1930. The prototype had a vertical sliding breech block design and was automatic. Upon firing, the recoil of the gun would open the breech and eject the spent casing out its rear whilst an autoloading mechanism would insert the next round into the empty breech, after which the action of the gun sliding back into place would close the breech once again, leaving the gun ready to fire once more.

While proving the potential of the design, the prototype failed to meet the specified rate of fire requirement of 130 rounds per minute. It wasn't until 1934 that a production model, 40 mm L/60 Model 1934, was ready. In the following years, minor improvements led to the development of 40 mm L/60 Model 1936, which would finally be accepted into Swedish service as 40 mm/60 Model 1936. Despite its name, the barrel length of the 40 mm L/60 Model 1936 was actually 2250 mm (56.25 calibres).

The British Army first purchased 100 Bofors guns in 1937 for examination and testing which were found to show satisfactory performance. However, many parts of the gun as originally designed were intended to be fashioned or fitted by hand, limiting the rate of production to a pace that couldn't possibly meet British demand. Thus, Britain acquired a licence to produce the gun domestically. Changes were made to the design to streamline mass production, including the conversion of measurements from metric to imperial. These changes not only vastly improved production efficiency, but they also lowered production costs.

The Mark VII mount is a single mount that uses a British-produced Bofors gun. It was operated by two crewmen, a gunner and a loader. Sitting on the left side of the gun, the gunner trained and elevated the gun, which was hydraulically driven and had elevation limits of -10°/+90°. He was also in charge of firing it. The loader, who stood on a platform just behind the gunner, was, of course, tasked with the loading of ammunition into the gun.

SAP, AP, and HE rounds were produced for the British Bofors guns, each weighing 0.894 kg (1.97 lbs.). Both SAP and AP were painted black with white tips, with AP being distinguished by a white ring painted on the body. HE, painted buff, had 0.068 kg (0.15 lbs.) of TNT and self-destroyed after travelling for approximately 3,200 m (3,500 yds). Rounds with tracer were indicated by an additional red ring. At the right of the gun was a ready-use ammunition rack with a capacity for six clips each. Ammunition was loaded by the crew through the top of the gun into an ammunition "hopper", from which the automatic loader pulled the ammunition from. Spent cartridges were ejected out of the rear of the gun, down chutes redirecting them under the guns towards the front where they can be ejected safely away from the crew. Altogether, the Mark VII single mount weighed 1.42 tonnes.

The Mark VII single mount was introduced very late into the war, around May 1945. The Royal Navy estimated that the Bofors gun was about as effective against kamikaze aircraft as their domestic design, the Vickers 2-pdr Pom-Poms, but they found that the Bofors gun was about twice as effective against bombers. After WWII, the Mark VII mount gradually replaced the older, hand-cranked Mark III single mount, seeing use on many Royal Navy ships, as well as some limited usage by the Royal Australian Navy, as late as the 1970s. It's a testament to the gun's effectiveness as an anti-aircraft weapon that it remained in service for so long, hindered only by the arrival of the jet age.

Media

Excellent additions to the article would be video guides, screenshots from the game, and photos.

See also

• Bofors (40 mm) (Family)

External links

• NavWeaps - USA Bofors 40 mm L/60 Model 1936
• Wikipedia - Bofors 40 mm gun