I'm by no means a pro, but my first introduction to organized matches other than early Naples Swamp Romp were the North Carolina Tactical Matches Kyle Lamb put on the the mid 90s...he shot reasonable scenarios that necessitated securely attached ammo...in and under autos with rifle and shotgun... I shot the first match with a 26" Rem1100 and was looking for a hacksaw on the way home...even the Ft Benning matches starting in 2005 the long range was realistic for a 5.56 at around 418m for a 4x scope and good ammo, and doable with a 16" mid....I had a 12th place finish on the long range stage in 2009 at age 62... the advent of Three Gun Nation changed the look of the shotguns...as others have commented, depends on where you shoot... down here a 16" mid with good ammo works, and I'm ready for another of Kyle's Ford Tiempo props