Welding thick high hardness introduces a large number of problems into the manufacturing process. As a result, a significant number of early T-34s had manufacturing defects, chiefly cracks in the armour near the welding seams. Defective hulls and turrets as well as one complete tank assembled from defective parts were shot up in order to determine the effect of cracks on the toughness of the armour.
"Plan of trials of a hull and turret of a T-34 tank
Basis: BTU KA chief's letter #76105 on August 28th, 1940
1. Goal of trials
To determine the resistance of the design to shells, reliability of the joints between various parts and components of the hull and turret (welds and attachments of removable parts, hatches).
2. Characteristics of the object under trial
A production hull with a production turret is to be tested by firing. The hull must be assembled according to production blueprints described in order #260001. In addition, the following must be installed:
- Defective wheels with suspension arms and suspension springs, drive sprocket, idler, tracks.
- Final drive covers part # 34-16-003.
- Machine gun ball part # 34-26-20sb (sans machine gun).
- Observation devices parts #34-36-18sb and 34-36-21sb.
- Completely filled air tanks.
- Either defective radiators or a plywood model.
- One defective oil tank and rear fuel tanks.
The turret must be assembled according to production blueprints described in order #260001 and installed on a turret ring. In addition, the following must be installed:
- Defective gun shield with trunnions and elevation mechanism gear part #34-31-sb-1.
- Gun mantlet part # 34-32-1sb.
- Observation devices parts # 34-36-24sb and 34-47-sb-1.
- Pistol port plug part #34-30-7sb.
- Defective elevation mechanism.
- Defective traverse mechanism sans motor.
- Clamps part # 34-30-034.
- Travel lock part # 34-30-6sb.
Mannequins of the crew should be installed in the hull and turret in the crew seats.
3. Conditions of trials
Trials will be performed by firing the 45 mm gun from 50 meters and machine guns at hatches and observation ports. Before the machine gun is fired, it is necessary to install plywood shields to detect splash.
The muzzle velocity is to be maintained at stock.
Firing is to be performed against the armour at the angles that they are presented in the design.
Depending on the results, the commission has the permission to reduce the muzzle velocity, but not below the limit of partial penetration.
The number of suggested shots into each component is included in the attached list. The number of shots may be greater than this, but no more than the established amount of shots per square meter of armour. Shots spread apart by at least 3 calibers count as fair.
After every hit, the commission will inspect the damage and record it in a separate log.
The final conclusions will be given by the commission based on the results of the trials.
Representative of the Chief Designer, Morozov (signed on October 1st, 1940)
District Military Engineer, Military Engineer 2nd Class, Kozyrev (signed on October 2nd, 1940)"