Howdy, y'all.
Wes Thompson's public range in Holser Canyon at Piru has good (and fairly level) steel plate targets at 100, 200, 300, 400, 500, 600, and 750 yards, and one large steel target at 1,000 yards (but at a considerable up angle). The Deadwood Boys' cowboy long-range range, also in Holser Canyon, has steel targets from just over 100 to about 500 yards, and most of them have a fair amount of up-angle. All of 'em - public and private - are a hoot to shoot.
To get to Holser Canyon and all these wonderful ranges from greater Los Angeles, take Interstate 5 north to the 126 freeway. Go west on the 126 to the town of Piru (consult a map), then turn north and drive toward Lake Piru. Wes Thompson's has a large sign on the road where you turn off.