Alright.
bind f "vstr attaz"
set attaz "vstr attackab"
set attackab "set attaz vstr attackac; bind MOUSE1 vstr attackdrop; ut_echo drop"
set attackac "set attaz vstr attackab; bind MOUSE1 +attack; ut_echo regular"
set attackdrop "+attack; wait 2; ut_weapdrop; -attack; bind MOUSE1 +attack; set attaz vstr attackab; ut_echo regular"
That should work okay, although shoot and drop is toggled off once the weapon is dropped. So when you pick the sr8 up again, you must press f to toggle shoot and drop mode back on. Use the f key
Thanks to JRandomNoob from the urt forums.
Edit: I have not tested it though.
Also try messing with wait or removing it if neccessary. I think that that will work however.