The title refers to a symbolic ceremony that someone has passed from one stage of life to another such as with the Hebrew Bar Mitzah for passing from childhood to manhood
Just before moving on the courthouse, the Sheriff is assigning weapons and says, "Kenny, 37 millimeter." Today, 37mm. is the standard size for non-lethal ordinance like teargas grenades and concussive flash-bangs. On the lethal side, 37mm was a standard size for anti-aircraft and anti-tank cannons during WWII.