Can it apply?
Rapid Reload reduces the Heavy Wirst launcher from Full-Round reload to Standard. If you have proficiency in Hand Crossbows you're proficient with the launcher, but does it count as a crossbow for Crossbow Mastery?
By RAW it does not count as a crossbow because nothing says it counts as a crossbow. Item description in Ultimate Intrigue doesn't say so and it's not listed in the crossbows weapon group (I don't see it in any weapon group.)
I feel this is squarely in "ask your GM to make an exception for you" territory. But it's basically the "what weapon group is this in" kind of ruling, and "crossbows" is the most sensible place to put it IMO.