Bruce quite plausibly made the case that he shouldn't allow his own phobic reaction to the thought of using guns to prevent his Robin's from knowing how to handle firearms.
Dick apparently aced his marksmanship at Police Academy (Which would have been more interesting if Dixon had ever actually SHOWN us any of it, but let's not go into that)
We saw him train Jason here
We've seen that he trained Tim in how to use an unloaded gun as an impromptu throwing weapon.