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M24 in Norwegian Service A Norwegian M24 preserved in Akershus http://preservedtanks.com/Albums/Blog/20080917/P1000439_M24_Akershus_c.jpg The Norwegian military received its first M24 Chaffee tanks in 1946, when a batch of nine tanks arrived (some sources say that 17 arrived total, of which 8 were used for training only). By the 1950s, a total of 123 (some sources say 124 or 125). These tanks were adequate for their role in the 1950s, but by the middle part of the Cold War, it was apparent that they were outdated. In particular, the 75mm main armament was wholly inadequate against newer Soviet tanks such as the T-54/55 or T-62. However, acquisition of new tanks to replace the M24s would have cost a great deal of money which the Norwegians did not have an excess of. As a result, it was decided to modify the Norwegian M24s to improve their combat capabilities. Development of NM-116 Development of what became the NM116 began in the late 1960s. It was decided that the M24s would be upgraded completely; not only would new armaments be fitted, but a new powertrain, advanced fire control system, and other equipment would be added. Also, it was decided that the new tank would be used in the antitank role by the Norwegian Army. Trials of the first prototype of the upgraded M24 began in January 1973, and after several months of testing, it was accepted for production. Norwegian engineering firm Thune-Eureka was selected as the primary contractor. However, numerous other companies, such as Cadillac, also participated in the program. Around this time, the new tank received the designation NM-116 (also written NM116). It was commonly referred to as the NM-116 Panserjager, due to its use in the antitank role. The NM-116 was heavily modified, with a new main armament, fire control, engine, and other systems. The crew had also been reduced from five to four, with the elimination of the bow gunner position. An NM116, easily distinguished from an M24 by the different armament, turret, and laser rangefinder. Diagram showing the crew layout of the NM116 Teknisk Håndbok Panserjager NM116 Pg. 3-3 Seventy-two M24s were upgraded to the NM-116 standard in total. Eight of the remaining Norwegian Chaffee’s were modified become the NM-130 Bergepanser, an armored recovery vehicle. These upgrades took place from 1973 to 1977; the upgraded tanks were grouped into six units of twelve tanks each. These supplemented Norway’s Leopard 1 tanks, which entered service in the late 1960s / early 1970s. The NM-116’s remained in service through the latter years of the Cold War, not retiring until 1994. Though the tanks never saw combat, they still formed an important part of the forces on NATO’s northern front. http://www.spycom.org/11_KALD_KRIG/materiell/116.jpg Upgraded Equipment Main Gun By 1973, the 75mm M6 obsolete as an anti-tank weapon. However, the relatively small M24 would be unlikely to handle a full power 90mm or 105mm anti-tank gun without seriously damaging the tank every time it fired. As a result, it was decided to acquire the French 90mm D-925 gun. This gun operated at a lower pressure than guns such as the 90mm M3, producing less severe forces on the mechanism and less recoil. However, it also meant that the projectiles fired would have a lower muzzle velocity. This forced HEAT shells to be used as the primary antitank rounds. The D-925 as mounted on the NM-116 could fire three kinds of rounds; Hulladingsgranat M62 (Hollow Charge Shell / HEAT) Projectile Weight: 3.650 kg Projectile Length: 0.5m Explosive Filler: 0.67 kg Muzzle Velocity: 750 m/s This round was capable of penetrating up to 320mm of armor, or 120mm against a plate angled 65 degrees from vertical. Technical manuals state the round would fail to fuse at angles over 70 degrees. Sprenggranat MF1 (High Explosive Shell) Projectile Weight: 5.280 kg Projectile Length: 0.48m Explosive Filler: 0.945 kg Muzzle Velocity: 640 m/s Røykgranat MF1 (Smoke Shell) Projectile Weight: 5.40 kg Projectile Length: 0.48m Phosphorus Filler: 0.800 kg Muzzle Velocity: 635 m/s This round could make a smoke cloud 50m across that would persist for 20-30 seconds. There was also a practice round with the same ballistics as the HEAT shell. The gun was capable of elevating 15 degrees above horizontal, and could depress 10 degrees. Normal recoil length was 280mm, with a maximum recoil of 317mm. Ammunition capacity was 41 rounds. In addition to the D-925, an M2 Heavy Machine Gun was mounted in the turret, coaxial with the main armament. 1500 12.7mm round were carried within the tank. The NM-116 was also fitted with a smoke discharging system, firing 76mm smoke grenades. 16 smoke grenades were carried, and up to 8 could be launched at one time. Diagram showing new turret, with main armament, smoke launchers, etc. Teknisk Håndbok Panserjager NM116 Pg. 3-38 Fire Control The M24’s analog fire control was augmented by a Simrad LV3 laser rangefinder. This allowed more accurate determination of range, improving accuracy. Engine/Powertrain As part of the NM116 upgrade program, the M24’s twin V8 engines were replaced with a single Detroit Deisel 6V53T engine. This six cylinder engine produced more power than theprevious installation, but was smaller and more reliable. With the new engine came a new transmission, the Allison MT 650/653, a 6 speed automatic transmission (5 forward, 1 reverse) with torque converter. A new cooling system developed by Thune-Eureka was fitted as well. The installation of new engines and transmissions made the NM116 more reliable than its predecessors, and somewhat improved mobility and fuel consumption. Other Upgrades The NM-116 modernization program included the installation of numerous minor upgrades and improvements to the M24. One of the most notable of these was the radios. Tanks assigned to platoon leaders were equipped with an AN/VRC44, while other tanks were equipped with the AN/VRC64. A new intercom system was also fitted in the tank, as the crew layout was changed from the standard M24. Specifications: Dimensions of NM116 Weight: 18300 kg Length (gun forward): 5.92m Length (gun rear): 5.32m Width: 2.82m Height: 2.60m Ground clearance: 0.45m Ground Pressure: 74 kPa (.74 kg/cm2) Maximum Speed: 47 km/h (governed) Range: 300 km Engine Power: 260 hp at 2800 rpm (191 kW) Torque: 735 Nm Ammunition Capacity: 41 rounds Sources: http://modellnorge.no/nyheter-mainmenu-2/forbildenyheter/402-panserjager-nm116-historie-og-kamuflasje Zaloga, Steve, and Jim Laurier. M24 Chaffee Light Tank, 1943-85. Oxford: Osprey, 2003. Print. Page 22 http://modellnorge.no/images/stories/th/nm116th/index.html#/0 - Teknisk Håndbok Panserjager NM116 http://www.detroitdieselpartsdirect.com/Documents/detroit-diesel-specs/6V53T-Industrial.pdf http://www.primeportal.net/tanks/erik_torp/nm_116/ - Numerous pictures of NM-116 http://modellnorge.no/index.php/galleri/militaere-kjoretoy/militare-kjoretoy/nm116-nm130-og-m24-chaffee- Pictures of NM-116, NM-130, and Norwegian M24s