depends, do you plan on humping a lot of territory w/ your HBAR? if so, the i would opt for the govt profile...
just so, some prefer the looks and weight of the HBAR and the govt respectively--its all on the person
the slimmer bbl of the govt should disperse heat FASTER b/c it has less metal retaining the heat; h/w, it would also heat up faster b/c it has less material to heat up...
HBARs take longer to heat up, but once heated up, they also take longer to cool down
all bbls will loose accuracy w/ extended firing--but it would take a lot of constant firing
firing the same # of rounds, i would say that the above would happen
as to semi auto ARs and heat build up, it depends on how much ammo you shoot, how fast you shoot, and how long you shoot....inaccuaracy will happen in either one eventually
but if you are shooting that fast, then i dont think that YOU will be that accurate anyways....
you could opt to have the bbl profiled, or you could just replace your bbl w/ a gov bbl and sell the HBAR