Most shotguns with 18-20" barrels have a plain ol' cylinder bore with no choke. Is that a problem? There is some debate about whether defensive style shotguns loaded with buckshot can even benefit from choke tubes. We fired some test patterns to find out. Like... a whole bunch of 'em. Four different buckshot loads, four different choke sizes at five-yard increments from 5-25 yards.
A couple of related videos in case you missed them:
Shotgun Hack Job: Budget DIY Home Defense: https://www.youtube.com/watch?v=VhLaLtK_RtI
Stuff You Should Know About Buckshot Part 1: https://www.youtube.com/watch?v=3haq5BFh7qs
Stuff You Should Know About Buckshot Part 2: https://www.youtube.com/watch?v=Jf4i8gRTsJs