The A-31 (R) Self-Propelled Artillery was originally a heavy Russian artillery piece, captured by Finnish forces during the Winter War. After problems were found with the original chassis, the designers of Nucleana stripped and rebuilt the suspension and transmission, taking the same 6.5-Liter I6 diesel setup as used on the T-20 and it's derivatives. As it shares the same caliber with the home-designed A-24 artillery, the breech was only slightly modified to accept the same shells, allowing the A-31 (R) to be fielded rather rapidly to assist the Finns in the conflict.
Sharing the same role as the A-24 Self-Propelled Field Gun, the A-31 (R) sports somewhat heavier armor in comparison and a thick fixed gun shield, allowing it to withstand much heavier punishment in comparison to the A-24. However, this does come at a cost to mobility, with crews finding the A-31 (R) more difficult to handle in the turns and on rough terrain at higher speeds. A not-insignificant number of A-31s were shipped back to Finland after being modified by Nucleana, with only a handful really remaining with the island nation.
- Heavy armor allows for better survivability under fire
- Extremely good High Explosive payload
- Boiling vessel comes standard, naturally
- Heavier weight leads to poor handling and a lower top speed
- Extremely vulnerable to overhead fire due to being open-topped
- Very limited gun traverse arc
- Little anti-infantry protection
- Slow reload on the gun and limited ammunition