Following the design review, Eng. Col. Alymov, chief of the Self-Propelled Artillery Office of the Red Army’s Main Armor Directorate (USA GBTU KA), and Eng. Lt. Col. Kovalev, chief of the 3rd Department of the USA GBTU KA, prepared a report that was dated June 25, 1943:
On review of the design, it was determined that:
1. Manufacture of the 203 mm self-propelled gun based on assemblies from the SU-152 self-propelled gun currently in production is quite feasible.
2. The maximum use of assemblies from the mass-produced SU-152 self-propelled gun will enable inexpensive production of the proposed self-propelled gun to begin in the near future.
3. To reduce the total weight of the entire system, the armor thickness may be reduced in the M-17 design.
4. The basic load of the M-17 contains four fewer rounds than the SU-152 (16 rounds vice 20 in the SU-152), which is important because the 203 mm round is much more powerful than the 152 mm round.
5. Rate of fire—one round in 80 seconds can be considered acceptable for this caliber.
6. The placement of the ammunition in the fighting compartment and the ease with which a shell is loaded and rammed are well planned, but a practical test on a prototype is needed.
7. The total weight of 45.8 tonnes for this chassis is at the limit, and the prototype must not exceed it under any circumstances.
Conclusions and suggestions
1. The M-17 203 mm self-propelled gun is more powerful than the 152-millimeter gun.
2. For destroying enemy defensive fortifications, it would be advisable to have self-propelled guns armed with 203 mm guns in addition to SU-152’s.
3. The weight of the M-17 self-propelled gun must not exceed the weight of the SU-152.
4. To verify the feasibility of using the 203 mm gun for self-propelled guns, I believe it advisable to build a prototype vehicle using Factory No. 172’s design, incorporating remarks by USA GBTU KA, and submit it for testing by GBTU and GAU so that a final decision can be made.{6}
These findings appeared to greenlight the project, and an SP assault gun with a 203 mm howitzer would finally take shape in metal. Or so they thought in the Self-Propelled Artillery Office—the artillerymen held an entirely different opinion. The main role of the M-17 was destruction of enemy fortifications, but some nuances emerged. Calculations for penetration by the M-40 howitzer’s shell revealed that at a range of 2000 meters it was 4% better than the ML-20. The two rounds were equal at 1000 meters, and the M-40 was 6% better at 200 meters! And those were the ranges from which concrete bunkers would be fired on. Thus, the rationale behind the M-17 was called into question, as reflected in a letter from the GAU’s Artillery Committee on July 26, 1943:
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The advantage is negligible and does not justify bringing a new system into the inventory.
The concrete-piercing action of the projectile of both the 152 mm gun-howitzer and the M-40 203 mm howitzer is insufficient to destroy strong reinforced concrete structures. Achievement of this mission may only be possible with the B-4 203 mm howitzer model 1931 and larger calibers.
If the high-explosive effect is assessed, experience gained from the war shows that a single direct hit by a 152 mm shell is enough to destroy the strongest enemy earth-and-timber emplacement with seven layers, and the explosive action of the 203 mm shell is more than needed.
Therefore, the 152 mm gun-howitzer fully achieves its missions and meets the requirements of the Field Service Regulations that prohibit use of larger caliber guns when a tactical objective can be achieved with a smaller caliber.
The heavy 203 mm howitzer can be an auxiliary-propelled gun intended for powerful fire support of infantry and motorized units.
Since these weapons primarily fire from cover far from the forward edge of the battle area, their armor can be limited to light frontal and side plates for protecting the gun crew against shrapnel.
This system should permit high-trajectory fire, i.e., fire at angles of 60°–70°. Therefore, the auxiliary-propelled gun is a conventional field gun carriage capable of moving under its own power.
The weight improvement resulting from removal of armor made it possible to mount a more powerful gun.
The large-caliber self-propelled assault gun is assigned to destroy field fortifications at short range.
However, since a direct hit on a fortified position requires more than one shot, and that as quickly as possible, i.e., at a high rate of fire, the advantage falls to the 152 mm self-propelled gun howitzer, which has a practical rate of fire of two rounds per minute, as opposed to the 203 mm self-propelled howitzer’s theoretical rate of fire of one round in 80 seconds.
To summarize, the GAU’s Artillery Committee has come to the following conclusion:
1. The M-17 203 mm self-propelled howitzer’s firepower and shell offer no advantages over the SU-152 152 mm gun-howitzer in service with the Red Army.
2. The GAU’s Artillery Committee considers it inadvisable to manufacture a prototype of the M-17 203 mm howitzer and continue work on the design.
3. The GAU’s Artillery Committee believes it necessary to suggest that Factory No. 172 of the People’s Commissariat of Arms develop a design for the B-4 203 mm howitzer model 1931 (consideration given to mounting the BR-2 152 mm gun model 1935).
The project design should eliminate the powerful, all-round armor and limit itself to a light gun shield.
Increase the elevation angle to 60–70°. The total weight of the system must not exceed that of the SU-152 152 mm self-propelled gun-howitzer, i.e., 45 tonnes.{7}
E. A. Satel, chairman of the Technical Council of the People’s Commissariat of Arms, expressed the same opinion in his letter of July 28, 1943:
After analyzing the above, the Technical Council has concluded that the M-17 203 mm self-propelled gun proposed by the factory in its engineering design has no advantages in terms of its firepower and the effectiveness of its shell over the SU-152 152 mm self-propelled gun-howitzer currently in service with the Red Army. Therefore, there is nothing to justify bringing the new system into the inventory.
The Technical Committee of the People’s Commissariat of Arms hereby denies approval of the engineering design of the M-17 203 mm self-propelled gun forwarded with No. 2424 for development of engineering drawings and manufacture of a prototype.
The Committee proposes that work on development of the M-17 203 mm self-propelled gun with the ballistics of the experimental M-40 cease.
At the same time, given the Red Army’s requirement for a self-propelled gun armed with a more powerful cannon than the ML-20 152 mm gun-howitzer intended for destroying enemy high-strength reinforced defensive fortifications, I suggest exploring the possibility of developing the 203 mm howitzer model 1931 (with consideration given to the possibility of mounting the BR-2 152 mm gun model 1935), based on the requirement set forth in Artillery Committee finding No. 829360s.
Submit a conceptual design for approval with a detailed calculation of the stability of the self-propelled howitzer during firing by September 20 to the Technical Council of the People’s Commissariat of Arms, the GAU’s Artillery Committee, and the Self-Propelled Artillery Office of the Red Army’s Main Armor Directorate.{8}
