Dave King has taken hundreds of Deer on crop deprivation permits with the 308 win which works very well out to 600 yards at 700 yards Dave has also taken a few but at this distance the 308 is running out of stream with a 175 grain bullet. A 45-70 at 700 yards and well beyound, with those 500 or so grain bullet will still pass completely through them and kill quickly. The heavy bullets carry a lot of momentum and penetration, plus the large caliber leave a good size wound channel and is not velocity dependant to do so
