Wednesday, October 16, 2013

The Sherman Firefly was one of the most important Sherman variant

Outwardly, the Sherman Firefly VC series of tank destroyers looked every bit like their M4 Sherman base counterparts. Closer examination however would reveal a system that was finally capable of dealing with the impressive German Tigers and Panthers at distance. The Sherman Firefly would go on to become one of the more important Sherman tank derivatives of World War 2.

The British and Americans were already looking into an upgunned version of the successful Sherman tank, seeing it that it was available in quantity with a progressive stream coming off the assembly lines at a record pace.

The Americans proposed mounting a 90mm main gun to the existing system but were later turned off to the idea of having to redesign an entirely new turret for the new system. Not to leave well enough alone, the British continued to believe that the upgunned Sherman variant was a viable cause an proceeded to mount their own 17-pounder gun into one of their many Shermans in stock. With a new turret design and a little modification to the base Sherman design, the Sherman Firefly was born - this Sherman mounting an impressive 76.2mm main gun along with a single Browning-type 7.62mm machine gun. The Allies finally found an answer to German battlefield dominance.

From the outset, Allied tank crews were at a disadvantage when tangling with the well-armored German tanks, needing numbers and ingenuity to usually overcome their counterparts. This resulted in Allied tank crews zeroing in for a near-point blank hit to the side or rear of the German units. The Firefly now gave the Allies some punch at distance, with the Firefly able to effectively engage targets some 1,000 yards away. As more impressive munitions became available in the latter months of the war, the destructive power of the Firefly became ever moreso something for Axis tank crews to contend with. So definitive was the arrival of the Sherman Firefly that German anti-tank crews and tanks received explicit orders to engage and eliminate Fireflys as the first priority in any given engagement.

The British converted some 600 of their basic M4A4 Sherman tanks into Fireflys with some 160 landing into the hands of American forces. It should be noted that these conversion models basically inherited the armor protection of their base M4A4 models meaning that no additional armor protection was given to the new Firefly design. As such, Firefly tank crews would still have been wary of their own safety when in the line of enemy fire. Fireflys would appear in the Normandy beach landings of 1944 and were later attached to standard tank battalions onwards, though it was initially seen that Fireflys would be fielded as their own squadrons.

Monday, October 14, 2013


OTs-12 "Tiss" compact assault rifle (manufacturer's index ОЦ-12 "Тисс", also sometimes spelled as OC-12 in English-language sources) was briefly manufactured during early 1990s by the TSKIB SOO (Central Design Bureau for Sporting and Hunting Arms, located in the city of Tula). It was intended for police use, and was closely based on the AKS-74U compact assault rifle, with main difference being usage of the large caliber, subsonic 9x39 ammunition, which provided significant stopping power and barrier penetration capabilities at short and medium ranges (up to 200-300 meters). Only several hundreds of OTs-12 rifles were made at TSKIB SOO in about 1993, but the mass production, which was anticipated at Tula arms factory, never commenced. Few OTs-12 rifles are still in use by some Law Enforcement units across the Russia.

The OTs-12 "Tiss" compact assault rifle by design is similar to the Kalashnikov AKS-74U rifle, featuring same gas-operated, rotary bolt action, as well as similar controls and furniture, including side-folding skeletonized buttstock. Main differences include new barrel with muzzle brake / compensator, new bolt and a new 20-round magazine for 9x39 ammunition.

Caliber: 9x39 mm SP-5, SP-6
Action: Gas operated, rotating bolt
Overall length: 490 mm (butt folded) or 730 mm (butt extended)
Barrel length: 200 mm
Weight: 2.5 kg empty
Rate of fire: rounds per minute
Magazine capacity: 20 rounds

Thursday, October 3, 2013

TKB-517 Korobov

German A. Korobov, Russian gun designer from Tula, began the development of assault rifles soon after the World War Two,when he designed the TKB-408 bullpup rifle for 1946-47Soviet Army trials. Despite the failure of TKB-408, Korobov continued the development of various assault rifles, both in bullpup and traditional configurations. During late 1940s, he tried gas delayed blowback action in his series of TKB-454 experimental assault rifles, all chambered for standard issue 7.62x39 ammunition. While these rifles displayed some good results in accuracy department, these also showed insufficient reliability. By the 1952, Korobov switched to the Kiraly-type retarded blowback action, with the two-part bolt that uses braking action of the lever, interposed between bolt parts and receiver. This action allowed for significant increase of accuracy, as well as simplification of design and production, compared to then-standard Kalashnikov AK assault rifles.

Korobov TKB-517 assault rifle. The small "tube" above the barrel is a cleaning rod.

During mid-1950s, Soviet Army initiates new trials for improved assault rifle design in the same 7.62x39 M43 caliber. Korobov submits his improved TKB-517 rifle, still based on the Kiraly type delayed blowback action; this weapon was extensively tested against modified Kalashnikov AK rifle, as well a number of other designs, and found to be superior to all. Korobov was found to be most accurate and controllable in full automatic mode (primary mode of fire, according to Soviet tactical doctrine), especially when fired from the shoulder or from the hip. It was also significantly lighter and less expensive to make than modified AK. Nevertheless, Soviet Army preferred less effective, but familiar and already well established Kalashnikov AKM over the more effective and lighter, but entirely new design.

TKB-517 is delayed (retarded) blowback operated weapon, that uses two-part bolt system, designed prior to WW2 by Paul Kiraly of Hungary. In this system, bolt has two parts -lighter breech block with breech face and extractor, and heavier bolt carrier. A two-arm lever is interposed between these two parts; lower arm of the lever rests against the receiver when bolt is fully closed. When gun is fired, pressure in the chamber forces the cartridge case backwards and against the breech face.Bolt begins to travel back, but the lever acts as a mechanical disadvantage,transferring the short movement of the light bolt to the longer movement of the heavy bolt carrier. This action is sufficient to slow down initial movement of the breech face before the bullet leaves the barrel. Once the pressure in the barrel is low enough, the lever breaks the contact with the receiver, and the rest of recoil cycle both bolt parts complete as a single unit. Similar system later has been used in the French FAMAS assault rifle.receiver of TKB-517 has been made from stamped steel, furniture was made from wood. Charging handle was attached to the bolt carrier at the right side. Safety/ fire mode selector was located above the pistol grip, also at the right side of the gun. TKB-517 used standard AK/AKM type magazines, including large-capacity 40 and 75-round ones, developed for RPK light machine gun.

Caliber: 7.62x39mm M43
Action: Delayed blowback
Magazine capacity: 30 rounds



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