M109A1 SPH
The M109A1 featured a new longer barrel, and various other improvements, with a maximum range of 18,100m.
M109A2 SPH
The M109A2 is a new production weapon which incorporated 27 mid-life improvements to the M109A1. The improvements provide for increased Reliability, Availability, and Maintainability(RAM) and safety characteristics as well as enhanced operational capabilities.
The M109A2 has the long tube M185 cannon installed in the M178 gun mount. The cab has a rear bustle rack which provides an increased ammunition stowage capacity. It has an all weather ballistic shield mounted over the panoramic telescope; counterbalanced travel lock and provisions for mounting the M140 alignment device.
M109A3 SPH
The M109A3 is a depot converted M109A1 incorporating the 27 mid-life improvements. The operational characteristics of the M109A3 are virtually identical to the M109A2. Some M109A3s have three contact arm assemblies: all M109A2 have five contact arm assemblies.
