In many entry points in Mexico, when you declare you gun, they take it and you have to pick it up when you leave. If you declare it in Enseneda and are cruising south, the only way to get it back is to go back to Enseneda and pick it up. Usually, it's not there anymore.
Kind of makes it impossible to declare a weapon and cruise
We had friends cruising the Eastern Caribbean and declared their weapon at every port. They were allowed to keep the gun with no problems. They said they thought they might have to present it but never did. Never even took it off the boat when they checked in. Just said they had it.
When we were in Venezuela in 02 cruisers were purchasing cheap fire arms for protection and when they left Venezuela or were going to be boarded they would throw it over the side.