The same setup was used on Canadian Shermans/ Centurians using .22 cal bullets before the age of laser pointers. Circa mid 50s to late 60s.
The crews would literally fire at small models, both static and moving. This was to practice their engagement/ crew drills in an IMR (Indoor Miniature Range).
Similar pictures are found in The Royal Canadian Armoured Corps:
An Illustrated History
http://www.rcaca.org/En/indexLM.asp?ID=8
I haven't seen pictures of larger caliber add ons before. Interesting.
Regards