1 acre that's kind of small for a rifle range I have 700 yard range on a 80 and it isn't long enough some times.
Design depends a lot on the lay of the land and what lies behind your range
Do live in a city now a acre of land in a city might seem like a fair amount put out in the country it really isn't.
Well if you make the shooting lane 40 foot wide one could get around 300 yards and still only use a acre but that doesn't give you any buffer on each side.
And I guess what you mean by using an acre.
Or are you considering a berm 208 feet long.