When the gang is chasing Rodney and Del in the Everglades, Rico somehow comes up with a rifle equipped with a scope, although there wasn't one in the trunk of the car.
Occhetti seems confused about where he would serve time if convicted. He says he doesn't want to end up in the "State pen," but its established that he is wanted by the FBI, which is Federal. Also, he states that he doesn't want to end up in San Quentin, which is in California.
When the hit man on the yacht assembles the rifle, he screws a silencer onto the barrel. He should know that a silencer won't work on a firearm that fires a supersonic projectile.
During the pursuit, the Cadillac driven by the gang performs some very violent maneuvers, but when the trunk is opened to secure the firearms, they are neatly arranged in the middle. When the car stopped abruptly, they should have been thrown to the very front of the trunk.