In 1941, the KV-1 was the most powerful tank on the battlefield, but it had major problems, such that more were simply abandoned because of mechanical failure than were destroyed by the Germans. As the shortcomings of the KV-1 became painfully apparent, new designs were proposed, going in all different directions. One of these was KV-7, also known as Object 227 and U-13. U, by the way, stands for "ustanovka," the Russian word for "gun." The KV-7 was a fixed casemate-type AFV with three guns built on the KV-1 chassis. The central gun was the same 76,2mm cannon of the KV-1, flanked by two 45mm guns. All the guns were co-axial, and could rotate 15 degrees side-to-side. In hindsight, this seems like a pointless design, since it doesn't make for an effective tank OR potent self-propelled artillery. A slight improvement was KV-7-2, aka U-14, which was almost identical, but swapped the two 45mm guns for a second 76,2mm cannon. U-13 and U-14 suffered from the same shortcomings, and the next development was U-18, which put a 152,4mm howitzer into the casemate. I was unable to find any drawings of U-18, but in February of 1943, a practical execution of the design entered production as Object 236, better known as SU-152. This vehicle was produced very quickly, with somewhere between 670 and 704 vehicles (sources vary) built between February and December, when the same concept was moved from the KV-1S chassis to the IS-1 chassis, and the new vehicle was designated ISU-152.
Below are some pictures of my models of the KV-7, SU-152, and ISU-152:
Currently, the only additions I plan on making to this particular collection are Object 704, which was the same idea built on the IS-3 chassis, and the ISU-152K, which was a more modernised version introduced in 1956. I may eventually add U-14 (and U-18 if I can ever find decent blueprints), but not any time soon. Unless, of course, someone asks me to.