Yes, I meant 2 cannons.
I should clarify though.
If the cannon affects only weapons, then it is quite well balanced, even if the delay stacks and is "sticky"
If the shield delay is also included, this effect would be OP with a stacking "Sticky" delay... the "sticky" quality being the harder of the two to balance
By "Sticky" I mean that the delay persists even if a new card is played into the slot.
If the effect only stacks but isn't sticky, then playing a new weapon and shield can overcome it.
Otherwise, the only recourse is to use EA, immaterial weapons and shields, or bonewall (which was addressed previously).