Both my son's killed their first gobblers with the same 510 mini at age 7. The 18.5"barrel is a nonissue in my opinion, but mine is a 20 gauge and threaded for choke tubes. Hevishot choke tube and Magnum Blends was the hot ticket in our gun. The 510 has single handily has taken more gobblers that any other single gun in my collection. I love shooting gobblers, but love watching my son's shoot them more!
TSS wasn't available when they started hunting, so 410 wasn't really the option that it has become today. 20 gauge on the Caldwell Field Pod was the trick for us.