IF XM885 does a 12/1 L/D Ratio then the current in-game rod dimensions should easily be buffed.
Currently 26x270, if this document was to be believed then at least the dimensions should be 26x312.
That’s also goes without saying the two different velocities mentioned, 1600m/s and 1661m/s.
1661m/s with 2-pound penetrator and 1600m/s for 3-pound.