What I recall, and @AeriaGloria can verify, is that the OFP2 is newer and weighs more, but also has a more potent engine to balance out the added weight. Before the last update, the simulated OFP2 did not have that extra powerful engine and therefore had quite crappy ballistics, which lead to different range tables. Now it should behave closer to the KOM, but will still differ, so use the KOM tables, but you might have to dial it in to fit the OFP2 ballistics better.
Marsvinet's post in Any way to move the heading bug in the HSI was marked as the answer