I think Hunting and Military weapons are the same calibers. . .assault rifles are usually light end rifles, but not always. Though this is usually a 5.56mm to 7.62mm comparrison, you can also have a heavy assault rifle firing 7.62mm rounds, and a .223 (5.56mm) hunting rifle, reversing the "Which is heavier" question. . . .they both cover essentially the same range of round sizes.
The major difference is the soft lead hunting round vs the full metal jacket round.
A lot depends on what nick selects to be the standard round, and in later books compares to it. (I guess you could just declare up front that all military weapons like assault rifles use FMJ and are rifled to use them, and make the mods now, while all civilian hunting weapons use soft lead rounds, and include the mods for that now. . .and leave the issues of hollow point and magnum for later.)
(If nick says FMJ is the standard, than SL hunting weapons should get a range and damage boost, and an armor penalty. If he says SL is the standard, then the FMJ rounds should get a range penalty, damage reduction and an armor bonus. The answer to your question is dependant on which is the standard.)
Since nick said he didn't want to get into specialized ammo variations, my call would be "No difference".