I. Am giving up on the time finding a reasonably priced 308. So am using a 1976 bar and going after market tactical cool and cutting the barrel. As far as a zombie shoot out, its buck shot all the way
The ATRS modern hunter is s straight pull bolt action. Not a semi automatic. Dam nice gun though.
I wouldn't cut the barrel, you may end up making it unreliable, the gas system is designed to have a certain amount of barrel past the gas port to give it the energy it needs to cycle.
I would look at the FN FNAR, it's the same operating system as your BAR in a modern package and can do very close to 1 moa with good ammo. It is also cheaper than all the non restricted rifles mentioned so far in this thread.