ok i got the classic
#showtooltip Arcane Missiles
/cast [nochanneling:Arcane Missiles] Arcane Missiles
to not interrupt missiles while channeling but it works only when u try to spam AM.
my question is, is there a macro to not interrupt missiles while u channel them and u press AB for example? cause sometimes im too fast and i interrupt em too soon to start casting AB again and as a result i get 4 missiles and not 5.