Pg 55. of the BRB
"Some missile weapons enable their users to shoot several times in each shooting phase - known as multiple shot."
The multi shot rule only mentions multiple shots in the shooting phase. S&S takes place in the movement phase. Therefore no multi shot as a charge reaction.
I have to say that I dont agree, The quoted text is just preamble for the actual rules. Unfortunately they arent in italics so who is to say what is a rule and what is background?
Thanks to Akuma on Warseer for starting the original debate
http://warseer.com/forums/showthread.php?t=149287