[Ewen B]

I have seen some photos of these concrete walls being used by aircraft to protect others from the backblast of jet engines at air bases in later years.

I don't recall seeing a wall at Rivers AFB which is now tragically a hog barn. Two of the hangers long since burned down, and many of the PMQ were moved to local communities. Not all CATP locations probably taught gunnery, so that could account for these walls not being everywhere.
Ewen