Bore evaculator, like on all British tubes from the 20pdr B tube upwards I believe. The strakes are an attempt at a counterweight I think.
Like I say, im only reporting what David Fletcher actually wrote. I seem to recall he related it was an attempt by the Jordanians to upgun them. I think he said it was done on their behalf by a British company, but I would have to search the article out.. I have no further information to comment further, other than I cant really see that one as being mistaken for a 105mm tube because it looks completely different from an L7. Unless an Israeli version of Sparky is responsible of course, which is always a danger.
Edited by Stuart Galbraith, 15 June 2018 - 0744 AM.