Type 38 anti-aircraft gun
| 37.5 mm L/70 Type 38 anti-aircraft gun | |
|---|---|
| <imgur w="300px">VVdY9DN.png</imgur> Black-and-white diagram of the Type 38 in the "Navy Type G" single mount. | |
| Type | anti-aircraft gun |
| Place of origin | Greater Menghean Empire |
| Service history | |
| Used by | Greater Menghean Empire |
| Wars | Pan-Septentrion War |
| Production history | |
| Produced | 1937-1945 |
| No. built | 8,000 (est) |
| Specifications | |
| Weight | 2,230 kg (including mount) |
| Barrel length | 2.625 meters |
| Crew | 8 |
| Shell | 37.5x250mm |
| Shell weight | 0.8 kg |
| Caliber | 37.5mm |
| Recoil | Hydro-spring |
| Carriage | Four-wheeled with twin outriggers |
| Elevation | -10° to +85° |
| Traverse | 360° |
| Rate of fire | ~150 rpm |
| Muzzle velocity | 870 m/s |
| Effective firing range | 4,000 m (effective slant range) |
| Maximum firing range | 8,120 m (maximum horizontal range) |
The 37.5mm L/70 Type 38 automatic anti-aircraft gun (Menghean: 37.5밀리 70구경장 38식 자동 대공포, sam-chil-o-sik milli chillyong gugyŏngjang sam-pal-sik jadong daegongpo), often shortened to Type 38 anti-aircraft gun in Tyrannian-language sources, was a Menghean 37.5 millimeter anti-aircraft gun used during the Pan-Septentrion War. Introduced in September 1937, it was used by both the Imperial Menghean Army and the Imperial Menghean Navy, and saw service in some of Menghe's puppet militaries during the late stage of the conflict.
Based on practical lessons from the first two years of the war and integrating features from a captured Rajian 40 ItK 35 anti-air gun, the Type 37.5 was a fairly advanced weapon by the time it entered service, on par with Casaterran medium-caliber AA weapons like the Bofors 40 mm gun. Some sources consider it the most effective AA weapon in Axis service, at least until the arrival of Bofors clones in Ostland and Dayashina, though throughout the war it was hampered by mediocre fire control systems. It was manufactured in single, twin, and quad mounts, with the latter used exclusively by the Navy.
Background
At the outbreak of war with Sylva, Menghe had no intermediate-caliber anti-air gun between the Type 26 12.5mm machine gun and the Type 17 75mm flak cannon. This was not unusual for 1935, as Rajland's own 40 ItK 35 was still a few months away from service, but it soon proved inadequate. The Navy in particular felt that the 12.5mm MG's effective range of 1 kilometer was too short to repel torpedo bombers effectively. The Army encountered similar problems during the land campaign in Innominada, though its commanders found that ground fire from dispersed machine-guns was generally adequate against early-war biplanes.
As an interim solution, the Navy removed from storage 120 single QF 2-pounder pom-pom guns which it had purchased from Tyran after the War of the Sylvan Succession, mounting them on heavy cruisers and battleships. Yet it regarded these weapons as obsolete due to their poor accuracy and low rate of fire, as well as the limited supply of stockpiled 40mm ammunition.
Anticipating the need for a long-term solution, the Navy submitted a requirement for a medium-caliber weapon capable of filling the gap between machine guns and dual-purpose flak guns. The weapon was to have a rate of fire in excess of 90 rounds per minute, a total mount weight of under 2,000 kilograms when on its mount, and an effective range in excess of 3,000 meters, while firing a heavy enough shell to disable or destroy any single-engine aircraft in one hit. These requirements would place it on par with the newest medium-caliber anti-air guns in Casaterra.
Development
The Design Bureau of the Insŏng Arsenal began work on the Navy's requirement in the summer of 1935, basing the layout of the weapon on Eisenmaat's successful 40mm anti-air gun already in service. In spite of pressure to have the weapon in service within one year, reliability problems with the feeding mechanism caused development to fall behind that ambitious deadline.
A breakthrough came in January 1937, when Army units in Themiclesia captured a Rajian 40 ItK 35 anti-air gun with minimal battle damage and were able to transport it back to Menghe for testing. The Insŏng Arsenal was particularly interested in the feeding and ejection mechanisms, which it integrated into its own design, replacing the cumbersome 10-round magazines which were initially planned. Testing on the modified prototype took place in July and August, and revealed very good reliability, with nearly identical performance to the captured 40mm gun.
The Insŏng final prototype was accepted for service in September 1937, which was the second month of the year 38 in the Menghean unification calendar. As such, it received the designation Type 38. It was rushed into mass production, with the urgency of new orders only intensifying after war with Maverica broke out in November. The first deliveries were made before the end of the year, with initial production prioritizing the Navy and more specifically its heavy cruisers and battleships. As production of the guns themselves was the main bottleneck at first, all of these early weapons were placed in single mounts. Deliveries to the Army began in mid-to-late 1938.
Description
Gun
At the time of its introduction, the Type 38 anti-aircraft gun was a state-of-the-art weapon, and it would go on to become one of the best medium-caliber anti-air guns of the Pan-Septentrion War. Both Menghean wartime tests and Allied post-war tests found the gun itself to exhibit comparable performance to the 40mm Bofors gun, with a higher rate of fire and a longer range but lower reliability and flawed fire-control.
Owing to its use of lightweight components in the receiver, the Type 38 could manage a higher rate of fire than the Bofors 40mm and 40 ItK 35 anti-air gun. The exact rate of fire varied with the gun's elevation, as the movement of shells downward in the feed mechanism was gravity-assisted, but it was reported to be 150 rounds per minute on average with a well-maintained gun. Furthermore, because the loading system allowed new five-round clips to be inserted into the feed while the weapon was firing, this rate of fire could be maintained continuously without the need to stop and change magazines. The high rate of fire did, however, contribute to high barrel wear and rapid overheating, problems which led the designers to artificially limit the rate of fire to 90 rounds per minute per gun on mid- to late-war twin and quad mounts.
Early-production models had a distinctive cage-type muzzle brake with four large apertures situated at 90-degree intervals. This was found to divert the muzzle flash and smoke excessively outward, interfering in the gun crew's ability to aim and operate the weapon. From about 1940 onward, a conical flash hider replaced the muzzle brake on all new-production weapons and was refitted to most old ones.
Ammunition
Five types of ammunition were produced for the Type 38 anti-aircraft gun, not including inert training cartridges for handling exercises. These consisted of a dummy training round with a tracer but no explosive filling; a high-explosive round with a tracer, contact fuse, and self-destruct fuse; an armor-piercing round; and two types of timed-fuse high-explosive shells with tracers.
Both timed types used non-interchangeable powder fuses, one for 1,000 meters and one for 2,000 meters. The theory behind this ammunition type was to fire two barrages of shells which would detonate directly in front of an approaching plane, either destroying it as it entered the flak wall or deterring it from its approach. Failure rates for the powder fuses were very high, about 15% during tests conducted in 1938, and target practice, combat experience, and mathematical calculation all soon determined that direct-contact shells were more effective than timed barrage fire shells. As such, production of both timed-fuse types ceased in March 1939.
While the timed-fuse shells were in production, Navy service mounts were issued three ammunition types: 2,000 meter timed, 1,000 meter timed, and contact-fused. All were carried in separate five-round clips color-coded to indicate the ammunition type. After the exhaustion of time-fused shells, contact-fused HE accounted for all ammunition on Naval Type 38 mounts. Army AA units were issued a combination of armor-piercing shells (for ground vehicles) and high-explosive contact shells (for aircraft and soft-skinned ground targets), also in color-coded five-round clips of a single type.
Army service
The vast majority of Type 38s deployed on land were Army G-type or Army N-type mounts. These consisted of a single gun, with or without protective shield, on a four-wheeled towed carriage with deployable outriggers for stabilization. This would be towed behind a utility truck carrying the gun crew and ammunition. With a well-trained crew, the mount could be brought into action in under a minute.
The Army also developed two self-propelled mounts for the Type 38. These were the Type 39 self-propelled anti-air gun, which used a halftrack chassis with a shielded gun, and the Type 41 self-propelled anti-air gun, which used a more enclosed but open-topped turret on a converted Sal-ho medium tank chassis. The former was issued exclusively to tank and motorized divisions, as it could better keep up with their advance. The latter was exclusively issued to armor units, and was very uncommon, with only about 120 units produced.
The Imperial Menghean Navy received high priority for early deliveries of the Type 38 anti-air gun, as by 1937 it was suffering repeated attacks from Sylvan land-based aircraft. Initially, these were installed in a combination of open single (Navy G-type), shielded single (Navy N-type), and open twin (Navy D-type) mounts. All three relied entirely on manual cranking for their elevation and traverse controls, which was a particular problem for the heavy twin and shielded guns. They also lacked separate fire-control directors, relying on vocal commands from a spotter assigned to the gun crew. This had the advantage of lightening the mount and allowing it to be bolted on with minimal modification - good features given the Navy's need for a rapid upgrade to existing ships. But it also resulted in poor accuracy, as vibration, noise, and muzzle flash all interfered in the targeting process.
The Navy arrived at a solution to these problems in the summer of 1940, introducing the Navy R-type mount. This was a twin mount resembling the D-type, but it had powered traverse and elevation controls, greatly improving its ability to track aircraft. These powered controls could be electrically linked to a separate fire-control pedestal, which could be slaved to two mounts at once and was generally mounted one deck above them. Early Menghean pedestal directors were fairly crude, consisting of a reflector sight with rudimentary markings for visually estimating the target's speed and range; they mainly served to separate the aiming point from the vibration and muzzle flash of the guns. The R-type mount still incorporated manual hand cranks to operate the gun if the fire-control pedestal became disabled. A variant, called the M-type mount, added a larger gun shield in front but was otherwise identical.
The highest development of the IMN's Type 38s came in the Navy B-type mount. This was a quad-barrel (2x2) mounting which first appeared in 1944. The loading trays were angled horizontally outward and used a chain-like mechanism to pull in cartridges, as gravity could no longer be used. Cartridges were still ejected out the back of the receiver, and the guns were timed to fire at opposing corners simultaneously so that spent casings from the upper and lower rows would not collide. The barrels had outer jackets for water-cooling, allowing longer sustained firing periods. The fire-control pedestal received an improved gyroscopic mechanism to help correct for ship movement and traverse speed, and the gun crew received reflector sights as well, in place of the simple iron rings used on all prior Army and Navy mounts. This weapon was markedly more effective than all preceding Naval AA guns, but it was also larger and heavier, making it harder to retrofit onto existing ships. It also gained a poor reputation among its crews due to the unreliable loading mechanism, the failure-prone traverse controls, and the cramped armored basket in which the large gun crew had to sit. Many of these problems were linked to the decline in manufacturing quality Menghe faced late in the war, as worn-out equipment, strategic bombing, and economic crisis undercut the country's ability to produce complex weapon systems. The Navy also received low priority in industrial planning after 1942, as the air and ground theatres were considered more critical to Menghe's survival.
At no time during the Pan-Septentrion War did the Imperial Menghean Navy combine a Type 38 mount with stabilization or radar, features which were starting to emerge on Allied 40mm AA guns late in the war. Partial blueprints found in Sunju illustrate what appears to be a Navy proposal for a radar-assisted fire-control unit much larger than the improved pedestal, but there is no surviving evidence that the IMN built a prototype of this system. Menghean radar was generally of poor quality throughout the war, and given the decline in Menghean industry after 1943, it is unlikely that the Greater Menghean Empire would have been able to pass a radar-aimed Type 38 mount into service before its surrender in November 1945.
Mounts
Army
- Army G-type mount
- Single gun on a four-wheeled trailer, the design of which was also copied from the 40 ItK 35. Most common Army version throughout the war.
- Army N-type mount
- Functionally identical to the G-type mount, but with a 5mm gun shield to protect the crew. Some G-type mounts were refitted to this standard.
- Army D-type mount
- Twin mount similar to the Navy D-type, which came first. It used a sturdier version of the Army G-type's four-wheel trailer.
- Army R-type mount
- Proposed modification of the Navy B-type mount for use in fixed fortifications, to defend cities or coastal installations. It would be mounted on top of a concrete bunker containing ammunition storage and aimed with the assistance of a separate fire-control pedestal. It was the only powered Type 38 mount in Army service.
- Type 39 self-propelled anti-air gun
- Utility halftrack with a single N-type shielded gun on the rear platform. Used in armor and cavalry units.
- Type 41 self-propelled anti-air gun
- Sal-ho tank chassis with an open-topped turret carrying a single Type 38 anti-air gun. ~120 built.
- Navy G-type mount
- Based on the Army G-type, this incorporated a sturdier mount to connect directly to the deck, and a curved panel at the end of the casing ejection tray to deflect cartridges down onto the deck. Like the Army models, it was hand-cranked, unstabilized, and could not be controlled by a separate director.
- Navy N-type mount
- G-type mount with a gun shield. The shield was different from the type used on the Army N-type, and covered the sides and top as well as the front. Some sources claim it was thicker, at 10 millimeters, and post-war testing by the Allies concluded that the heavy shield slowed down the manual traverse and seriously reduced visibility.
- Navy D-type mount
- Twin version of the G-type with a sturdier base. It incorporated the same manual control requirements as the G-type and lacked a shield.
- Navy R-type mount
- Powered twin mount introduced in 1941. It could be aimed automatically from a separate fire-control pedestal, or manually by its crew. The fire-control pedestal incorporated only crude rangefinding, windage, and target-lead controls and mainly served to separate the gunner from the muzzle flash.
- Navy M-type mount
- Variant of the Navy R-type with a gun shield (some sources call it a "half-turret") covering the front, top, and sides of the gun. This was found to restrict visibility somewhat, leaving the gun crew more reliant on separate fire-control pedestals.
- Navy B-type mount
- Late-war quadruple mount with a 2x2 stacked gun arrangement. The guns were rotated 90 degrees and used 10-round feed trays to the sides. Also the only Type 38 mount to incorporate water-cooled barrels. As production started in 1944, it was only used on a few ships, mainly refitted large cruisers.