Sort of new test grid Nevada

I was looking at the range ring found by nic and noticed this "new"grid that was built between 2003 and 2007. It appears to be a rectangle with 6 squares horizontal and 8 squares vertical. There are 12 trucks pretty much evenly spaced. There have been some test as you can notice a relatively tight "shot" group in 2011 imagery, guessing sub-munitions/cluster bomb?