Jim Lane in tail gun (.50 cal.) put in B-25 #81, summer of 1943, Chaukulia, India, as a field modification (see more about this modification here).
This should be B-25D-15, #41-30381, assigned to the 491BS/341BG while the unit was stationed at Chakulia.
(Thanks for the research and information supplied by Yves Marino and Tony Strotman.)