Do crossbow skills that fire very quickly crit on each bolt, or once for the whole clip? Specifically thinking about their interaction with Cast on Crit

I've yet to really use a crossbow, but seeing videos of skills like Shockburst Rounds and Rapid Fire made me curious. Can they can trigger Cast on Crit fairly reliably given how fast they fire? Or does a full clip of Shockburst Rounds, for example, count as just a single crit?