* T-26 with the A-43 turret:[56][57][58] artillery T-26 or “tank of fire support” with a turret developed by self-taught inventor N. Dyrenkov at the Experimental Design Office of the Department of Mechanization and Motorization of the RKKA (UMM RKKA). Two types of turrets, armed with the 76 mm regimental gun mod. 1927 and DT tank machine gun in a ball mount, were assembled by the Izhora Factory. They were partially pressed and welded. The first variety was installed on the T-26 mod. 1931 in February 1932 and the second type was used in November 1932 (in the last case, the rear armoured plate of underturret box was made sloping).[citation needed]
It was found that the A-43 turret was very tight for two crewmembers; it had insufficient observation field; there was no turret ventilation, which made continuous gunfire difficult; and it was hard to rotate the turret manually. At the beginning of 1933, a new 76 mm KT tank gun mod. 1927/32 with reduced (from 900 mm to 500 mm) recoil length was installed into the A-43 turret. The turret was still a very tight place for crew members. The ammunition stowage for 54 rounds was unsuccessful, and the military refused the A-43 turret.[56][57][58]
- T-26-4:[59] artillery tank with enlarged turret armed with the 76.2 mm KT tank gun mod. 1927/32 (some modern sources mention this tank as T-26A, A stands for artilleriysky or “artillery”). The turret was developed by the Bolshevik Factory (since February 1932—by the Design Office of the established Factory No. 174) in 1931–1932; it was installed on the T-26 mod. 1931 in November 1932. Unlike the A-43 turret, the turret by Factory No. 174 was much more convenient for the crew. The turret of the T-26-4 was quite similar to main turret of the T-28 medium tank.[citation needed]
The T-26-4 with the KT tank gun passed tests successfully and five vehicles were built in 1933–1934 as pilot batch. Initially it was planned to arm three of these T-26-4 with the 76.2 mm KT tank gun mod. 1927/32 and the other two tanks with the 76.2 mm PS-3 tank gun. The PS-3 tank gun was developed at the Experimental Engineering-Mechanical Department (OKMO) of the Factory No. 174 by engineer P. Syachentov. The PS-3 had better specifications in comparison with the series-produced KT tank gun and also had several technical innovations (foot firing switch, original training gear, travelling position fixing, binocular optical sight). The T-26-4 armed with the PS-3 tank gun was tested in October 1933 but it was found that the PS-3 was too powerful for the T-26 light tank—turret’s race ring and hull roof were deformed during gun fire, and the suspension springs were damaged. It was decided to arm the T-26-4 with the 76.2 mm KT tank gun only. All five experimental T-26-4 artillery tanks were tested during military exercises near Leningrad in September 1934 before scheduled series production of 50 such vehicles in 1935. But on 19 September 1934 an incident with a T-26-4 took place: a blow-back because of shell case destruction during gun fire. Despite the fact that this defect was unrelated to turret design, the military representatives cancelled the order to produce the T-26-4. Also the work to design turretless AT-1 artillery tanks armed with the powerful 76.2 mm PS-3 tank gun started at that time. The T-26-4’s turret construction was the design used in the series-produced BT-7A artillery tank.[59]
In 1939, the Armoured Directorate of the Red Army (ABTU RKKA) ordered the development of a new conical turret for the T-26 similar to the BT-7’s turret and to arm it with the 76.2 mm L-10 tank gun. Engineers of the Factory No. 174 felt it was impossible to implement this project because it would lead to a significant overload of T-26’s chassis.[59]
- 7.5 cm Pak 97/38(f) auf Pz.740(r): Ten Pak 97/38 anti-tank guns with shields were experimentally mounted on captured Soviet T-26 light tank chassis, resulting in vehicles designated 7.5 cm Pak 97/38(f) auf Pz.740(r). These self-propelled guns served with the 3rd Company of the 563rd Anti-Tank Battalion before being replaced by Marder III on 1 March 1944. ![AT-1 “Artillery Tank” based on T-26 hull ![]
. Artillery tank AT-1http://www.armchairgeneral.com/rkkaww2/galleries/T-26_5.htm. 
. self-propelled-gun-su-5-1 . self-propelled-gun-su-5-1 ![SOV - SU-5-2 (122mm