Cynthialee, I'm not quite sure you're grokking that this is a specific supplement for HeroQuest Prime, which has its own set of rules - some of those rules are vastly different than the base game. Trying to compare it to those base rules are, at best, useless, and at worst, a point of unnecessary tension. In this case, the crossbow DOES have a range restriction in HQP. That is all that matters. I believe "Firearms & Black Powder" was written with that in mind.
So, I understand where you're coming from. I really do, but let me see if I am also understanding what you're trying to say regardless of the comparison to the base game rules.
You're wanting to balance the Musket by making it have either 5 or 6 Attack dice, but also to require a reload action. This effectively makes the player only attack every other round, which I would argue is Not Fun. The player is only participating half the time that everyone else is. That's why I think the occasional "cleaning" plus the looming risk of the thing blowing up in your face is a better (and also similarly thematic) option. It makes up for the lack of reloading by also being fun and balanced. The player will still be put out of play every so often, but it's unpredictable, which is infinitely more fun than knowing you're useless every other round.
Yes, in reality the crossbow requires reloading, which also takes a long time to do. And this has been taken out of the game, because I think it's not fun to play that. Game design always rides the razor edge of trying to find the right combination of verisimilitude, simulation, abstraction, and fun. It's probably impossible for everyone to universally agree whether a particular mechanic works. But that's the wonder of playing and running games. You can houserule it however you like to fit your desired playstyle.