Six goal thriller ends in penalty disappointment.
It means that the U's have bowed out at the Second Round stage, when perhaps their performance merited further progression.
Sam Walker had already saved one penalty this season in the game against Peterborough, but he was unable to repeat his heroics this time around, as the Gills were clinical with their spot kicks.
Twice Tony Humes' men led in the game, before they then came from behind to take the match to a penalty shoot out.
The U's wait for a win in the Johnstone's Paint Trophy goes on, despite a lively encounter at the Weston Homes Community Stadium on Tuesday night. New loanee Elliott Hewitt made his Colchester debut in the right full back position with Craig Eastmond and Drey Wright the only other changes from the team that lost at Preston.
A vibrant and lively start to the game from U’s saw almost all possession in the attacking third, Watt was first beat the defensive line when he broke free on the left but his shot soared over the bar.
Minutes later Watt again found his way into the box but after going down under Jake Hessenthaler’s challenge, frustration was evident with a penalty claim dismissed.
The frustration was short lived as Drey Wright picked up the clearance and let fly from 30 yards out, the shot tickling the underside of the crossbar before settling into Stuart Nelson’s goal.
As U’s eased off the pressure following the goal, Gills capitalized. Brennan Dickenson intercepted a pass and accelerated beyond the defence and with just Sam Walker to beat, levelled the score.
Colchester picked themselves back up and forced Gills into conceding a number of set pieces, George Moncur came the closest to converting when his curled free kick was tipped over by Nelson.
It wasn’t long before U’s regained the lead. The move started with some superb playmaking from Gavin Massey in the middle of the park as he drove forward and picked out the run of Healey.
The striker darted into the box and when Callum Davies brought him down the referee pointed straight to the spot. Watt stepped up to convert the penalty kick and restored the U’s lead.
This time U’s stayed switched on following the goal and nearly went one better to add a third via Sean Clohessy, attacking down the left.
The play came from a wonderful display of team passing from back to front, Moncur from his own half spotted the run and once Clohessy was in behind the defence he chipped a shot just wide.
The U’s went into the break deservedly ahead, having played some of their best home football of the season. David Wright replaced Frankie Kent as the teams came back out for the second half.
Gillingham came out looking fired up for an equaliser, ten minutes in Bradley Dack managed exactly that when he converted Jermaine McGlashan’s low cross.
Healey came off to great applause following a real shift in attack with Freddie Sears now leading the line as U’s looked to gain the lead for a third time.
With fifteen minutes to play Gillingham grabbed another, giving them the lead for the first time in the game via Antonio German.
Drey Wright looked to have been fouled in the build-up but once Armine Linganzi was in the box he caused a scramble, with the ball eventually squared to German just in front of goal.
As Gills looked to settle on their lead it was U’s top scorer who spoiled the party three minutes from time. Hewitt to Sears was the combination and as the striker made no mistake in drawing U’s level.
Four minutes of injury time found no fitting dramatic winner for either side, leaving a penalty shootout to decide the tie.
Stuart Nelson the Gills keeper took the glory, with two penalty saves facing Tom Eastman and George Moncur before converting the winning penalty himself, ultimately knocking U’s out.