While the famous "Abrams" was always intended to use a 120mm gun (the deficiencies of the 105mm being known), there were a number of iterations which lead to this point. The M1 "improved performance" was one of the last major steps in the development of Abrams before the 120mm gun was fitted. The barrel is lacking its distinctive mass and fume extractor profile which usually serves as an easy identifying feature for modern Abrams.
There are a few other differences from the contemporary form of Abrams, for the aficionados to find.
~40k triangles. 2048x2048 texture for the whole vehicle body, plus some maps ranging from 32x32 for marker light emission to 1024x512 for the tracks. A collection of small textures shared with other vehicles, for markings and other miscelanea.
The game this is for is in active development and needs help in the form of testing, feedback from experts, and of course funding. Play the free public demo here:
https://gunnerheatpcdev.itch.io/gunner-heat-pc-development-test-build