If you measure a standard (factory declared) 18" Remington 870 barrel the way the ATF agent did...then the barrel would be 20.75".
Are you sure he wasn't setting you up?
JYD #123 The great one formerly known as Architect.
I am now a fictional British television police officer (currently a Detective Sgt) at Thames Valley Station. My governor is Detective Inspector Fred Thursday and it’s 1969.