With 140 grain Sierra gamekings @ 2900 FPS, it has over 1000 ft-lbs of energy at 600 yards, so yeah, it would probably be fatal if you managed to put one in the boiler room.
The heavier bullets don't fly as well, and fall below 1000 ft-lbs before 500 yards, and have a lot more wind.
Of course those bullets are still dropping about 10 inches every 25 yards past about 500 yards, so hopefully you get the range exactly right.
And hopefully you have a good zero at that range, at that altitude, because what your ballistic program spits out may or may not have any bearing on reality. Most likely not.
And hopefully what you thought was a 4 MPH wind at 30º isn't really 8 MPH at 45º, because that adds about 10 inches more drift at 600 yards.