Talking about clickety-clack 28 and 16 gauges overall lengths compared with break actions. On scaled to gauge receivers, the bolt doesn't have to travel as far on shorter length chambers to clear the ejection port. 12 and 20 gauge shells can be 3.5" for 12 gauge and 20 has 3" maximum hull length hence receiver needs to be longer than 16 or 28 gauges. However as I noted Fiocchi has announced 3" shells for 28 gauge. Not sure which gunmaker will accommodate the 3" shells.
PS: Benelli has announced a 3" 28 gauge

Last edited by GLS; 06/01/17 12:54 PM. Reason: PS added