I know we're not talking rifles here, but wouldn't it make sense that a 3" shell is closer to the lands and grooves than a 2 3/4" shell (assuming a 3" chamber). For me, in my Browning A-Bolt, 3" shells easily outperform 2 3/4" shells hands down. It will shoot 1.5" all day long with Federal Barnes Sabot loads.
Jim B.