You will want to show up an additional 15 mins early to wait by the TSA door, otherwise just checkin with the Allegiant agent like normal and inform them at you have to declare a firearm. They will make you sign a disclaimer stating it is unloaded and will ask you to open the locked case to put the signed disclaimer in it.
I add at least 30 minutes because every time I get a rookie and it's his or her first firearm and they use you for training practice. Very friendly about the entire process though.
No...each flight has line, but no line for special check ins. Just make sure you have time at check in, sometimes can run slow
Thanks! Your answer is awaiting moderation.