"Approved by the Deputy People's Commissar of Defense, Colonel General of Artillery Voronov
October 17th, 1942
Tactical-technical requirements for a 76 mm assault SPG
1. Purpose of the SPG
The 76 mm SPG is designed to support moto-mechanized units to combat firing emplacements, tanks, and personnel both with direct and indirect fire.
2. Requirements for the artillery component of the SPG
The SPG uses the stock rotating part of the ZIS-3 76 mm model 1942 gun. The ability to install a 57 mm IS-1 gun must also be retained.
The SPG must meet the following requirements:
- Practical rate of fire of no less than 12 RPM in direct fire and at small elevations.
- Gun elevation of at least +15 degrees.
- Gun depression of at least -5 degrees.
- Traverse range of 30 degrees (15 in either direction).
- The rate of traverse must be about 1.5 degrees per turn of the flywheel. The effort on the flywheel must not exceed 4 kg.
- The rate of elevation must be about 1 degree per turn of the flywheel. The effort on the flywheel must not exceed 4 kg.
- The recoil brake must be armoured. The armour must be 8-10 mm thick.
- The oscillating part of the gun and the recoil brake armour must be fully balanced.
- The bore axis height must be no more than 1650 mm.
- The gun position must allow for comfortable loading at all angles of elevation and traverse.
- The gun sight must be a mass production type either from the 76 mm regimental gun or the ZIS-3.
- Crew of 4 (including the driver).
During travel, collapsible seats for three men must be installed in the fighting compartment. - The gun must be rigidly fixed in travel and not move vertically or horizontally.
- The SPG must carry two PPSh SMGs.
- The SPG must carry 60 rounds of ammunition for the gun and 1000 PPSh rounds.
The ammunition must be stored in places that make it comfortable for the loader to work with, fix securely in its slots, and be easy to unlatch and retrieve.
3. Requirements for the chassis
The SPG must be built on a chassis that uses T-70 tank components. The SPG must meet the following requirements:
- The design must allow the installation of the 76 mm ZIS-3, 57 mm IS-1, and 37 mm AA guns.
- The maximum speed on a good road must be no less than 45 kph.
- The SPG must weigh no more than 10 tons during travel.
- The SPG must not exceed the height of 2000 mm during travel.
- The SPG must be stable when firing at a tilt, when facing downhill, or facing uphill at all elevation and traverse angles. Firing must be possible both on the move and at a standstill.
- The maximum slope that the SPG can climb on dry soil must be 30 degrees.
- The SPG must be able to cross a water obstacle 750 mm deep.
- The SPG must be able to drive at a tilt of 25-30 degrees.
- The fuel capacity must provide a cruising range of at least 200-250 km. The oil tank must carry enough oil to support a full expenditure of fuel.
- The gun mount must be armoured. The armour must protect the gun, crew, fuel tanks, and ammunition.
The gun and gun crew are covered from the front, sides, and rear.
Armour thicknesses:
Front armour: 35 mm
Side armour: 15 mm
Rear armour: 15 mm - The SPG's armour must guarantee:
- Secure protection of the gun and its crew.
- Comfortable and rapid entry and exit.
- The rear armour of the fighting compartment must flip out.
- The SPG must be equipped with communications equipment:
- A 12RP radio for external communication.
- A TPU-2 intercom for internal communication.
- The fighting compartment must have a path into the driver's compartment.
- The fighting compartment walls must have:
- Observation ports for observing the battlefield.
- Firing ports for firing the PPSh.
- In addition to ammunition indicated in section 2 paragraph 15, the SPG must carry the following:
- Pioneer tools: an axe, a saw, a crowbar, and a shovel.
- Tools and parts for the gun and chassis in a special rack.
- First aid kits and rations for the crew.
GAU Chief, Colonel General of Artillery, Yakovlev."