The M113 APC was initially modified to provide a carrier for the heavy 4.2″ mortar, and deployed in support platoons in infantry units. This version was designated as the M106, and later versions followed the upgrades of the basic M113 family. A version was produced to carry the 81mm mortar, the M125, but this was phased out of service in the US after the Vietnam war. It continued to be used by other nations, such as New Zealand. The 4.2″ mortar was replaced by the 120mm mortar, and the new version designated the M1064, with the appropriate suffix. Further information can be found at https://en.wikipedia.org/wiki/M106_mortar_carrier and https://www.inetres.com/gp/military/cv/arty/M106.html.
Other countries produced their own mortar carriers based on the M113 chassis. A typical example is Germany, using a different shaped hull top hatch, and different cupolas and smoke dischargers (optional).
The product includes hulls for the M106, M125, M1064, as well as the West German variant, with a separate rear panel/ramp. Separate models of some of the mortars that can be mounted are provided to allow the customisation of the hulls. Separate track assemblies are included, which should be printed with axles horizontal and ground contacting track surfaces touching the build plate. Supports in Cura should only be those touching the build surface, and 0.1mm resolution is recommended. A skirt is normally sufficient, but further support may be needed for the smaller components.
Further tests revealed that the idler wheel in the tracks did not print reliably (8th July 2019). Updated tracks (rev3) have been included in the relevant zip file.
The product is offered for personal, non-commercial use under the Attribution-NonCommercial 4.0 International (CC BY-NC 4.0).