QF Mark VII (40 mm)
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Description
The 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 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.
Other variants of the Bofors 40 mm gun within the game include:
- Bofors L/60 Mark 1: US-produced, water-cooled twin mount
- Bofors L/60 Mark 2: US-produced, water-cooled quad mount
- Bofors L/60 Mark 3: US-produced single mount
- 4 cm Bofors Flak 28: German captured single mount
- QF Mark V: British-produced, water-cooled twin mount
- QF STAAG Mark II: British-produced, water-cooled, and radar-guided twin mount
- Bofors (40 mm): Army version, mounted on various US and British anti-aircraft vehicles (SPAA)
- M266: Bofors 40 mm L/70 (increased barrel length and rate of fire), mounted on M247 Sergeant York
Vehicles equipped with this weapon
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 | |
| HEF-I | _ | _ | _ | _ | _ | _ |
| AP-T | 80 | 77 | 66 | 57 | 50 | 45 |
| Shell Details | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Ammunition | Projectile Mass (kg) | Velocity (m/s) | Explosive Type | Explosive Mass (kg) | TNT Equivalent (kg) | Fuse Delay (m) | Fuse Sensitivity (mm) | Normalization at 30° | Ricochet | ||
| 0% | 50% | 100% | |||||||||
| HEF-I | 0.9 | 881 | Tetryl | 0.068 | 0.0986 | 0.0 | 0.1 | _° | _° | _° | _° |
| AP-T | 0.882 | 874 | N/A | N/A | N/A | N/A | N/A | _° | _° | _° | _° |
|
Tetryl is equivalent to 1.45x TNT. |
Comparison with analogues
All naval Bofors 40 mm guns are virtually identical, the only difference between them being the rate of fire: all single mounts fire at 160 rpm, while twin and triple 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 virtually continuous fire. In other words, their cyclic rate of fire (mechanical rate of fire) is practically the same as their effective rate of fire (rate of fire with reload times taken into account). All naval Bofors 40 mm guns can jam if fired for too long.
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 (1000 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 (0.0274 kg 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 (845 m/s) and HE round (815 m/s), have a weaker AP round (67 mm @ 10 m, 0°) and a weaker HE round (0.04403 kg TNT equivalent), and have a lower projectile mass for both their AP round (0.7 kg) and HE round (0.623 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.
- 70-K (37 mm): The 70-K has a higher muzzle velocity for its HE round (880 m/s); but it has has a lower rate of fire (150 rpm), has a lower muzzle velocity for its AP round (880 m/s), has a weaker AP round (79 mm @ 10 m, 0°) and a weaker HE round ((0.05698 kg TNT equivalence), and has a lower projectile mass in both its AP round (0.758 kg) and HE round (0.72 kg). 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) and have a lower projectile mass in their AP round (0.91 kg); 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 (0.071 kg TNT equivalence), and have a lower projectile mass in both their HE round (0.82 kg). 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 while sitting safely outside the maximum range of almost every other smaller autocannon (most notably, the German 2 cm/65 C/38 with its 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 of the damage of the HE rounds. 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, since armoured targets are much more effectively dealt with using the destroyer's main armament.
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 breach and eject the spent casing out its rear whilst an autoloading mechanism would insert the next round into the empty breach, after which the action of the gun sliding back into place would close the breach 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°, and was 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. Ammunition for Bofors guns came in 4-round stripper clips, with both HE and AP clips being produced. To the right side of the gun was an ammunition rack with a capacity for six such clips. The loader placed ammunition clips into the gun's automatic loader at the top, which stripped the rounds itself. Like many other Bofors gun mounts, spent casings were ejected out the rear of the gun and guided down chutes directed towards the front of the gun, where they could be safely flung aware from the crew. In total, 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 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. Post-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
An excellent addition to the article would be a video guide, as well as screenshots from the game and photos.
See also
External links
