The NRA does allow guns at its convention. You can walk around all day with a loaded gun on your hip and nobody will say anything to you. Except maybe nice gun.
The only time you are not allowed to carry is when the Secret Service closest a venue for one of their protecties to speak.
There have also been venues such as stadiums where a concert was held where the stadium had a rule against guns. I don't go to those events because I carry everywhere.