I just checked... my cool find "Phantom Acres" is inside R-2524, which I am not sure is ever open.
But go check it out on Google Maps "Satellite View". Go about 25 miles north and slightly west of Barstow, CA, and look for three dry lakes right next to each other. Two medium sized lakes and one small lake in between them. These lakes are well East of the large dry lake that looks like South America (Cuddeback Dry Lake). I mistakenly called the 3 lakes the Cronese Dry Lakes but I had them mixed up with other ones... I think it is called Superior Dry Lake. No matter.
Go a mile or two north of the 3 small/medium dry lakes and zoom in, you will see an airstrip oriented SW-NE and a large rectangular parking ramp just north of the strip. Zoom in and you will see six or eight dead F-4's, some on the runway, some in the revetments, some in the big parking ramp. It is all a graded dirt (or "desert mix" pavement) simulated enemy air base for targeting and tac/nav practice.
Speaking of Cuddeback dry Lake, there is a small paved military runway just East of the lower tip of that lake. It was used for some helicopter testing back in the day, and it looks like a small municipal airport, but you will not be welcome if you land there. I had this strip marked on my chart (for an emerg. landing spot) at a glider race briefing once. An AF test pilot happened to see it, and took the chart right out of my hands and walked off with it!