Robbie Brady provided the breakthrough for United after almost half an hour of resolute defending by the home side, curling a left-footed free-kick through the wall and in via the goalkeeper's hands. The Irishman netted again in the 34th minute with a toe-poke, after Scott Wootton's flick from a Magnus Eikrem corner ricocheted his way off an opponent.
Bury pulled a goal back seven minutes before half-time when Kyle Bennett intercepted a Reece Brown pass in the centre circle and raced away to feed Danny Carlton for a low finish. But although the Shakers came flying out of the traps for the second period, with a shot from dangerman Bennett deflecting wide only 20 seconds after the restart, United's abundance of young talent eventually told.
Granted, England Under-19 goalkeeper Sam Johnstone had to be alert to keep Bury at bay - his best save coming when another Bennett effort bounced up off the turf just inches in front of him - but the Reds always looked the more likely victors.
Nicky Ajose almost made it 3-1 when he struck the post from a tight position on the byline; eventually it was Marnick Vermijl who restored the Reds' two-goal cushion, a minute shy of the hour, with a goal that will haunt Richie Branagan. The Bury keeper beat two United players to meet Brady's ball over the top but he spilled it