With the Cornhuskers backed up inside their own 1 late in the third period, Armstrong dropped back into the end zone threw the ball more than 40 yards to a wide-open Quincy Enunwa, who raced down the field, breaking one tackle for a score that put Nebraska ahead 24-12.
The Cornhuskers (9-4) survived a 25-yard fourth-quarter touchdown pass from Hutson Mason to Todd Gurley for Georgia (8-5) and a late drive deep into Nebraska territory to claim the win.
Enunwa and Armstrong teamed up for an earlier touchdown pass that helped Armstrong go 6-of-14 passing for 163 yards. Enunwa caught four of the six completions for 129 yards.
Georgia scored first, with Marshall Morgan making a 39-yard field goal, but Enunwa and Armstrong's first touchdown pass -- a 5-yarder -- came just 92 seconds later and the Cornhuskers never trailed again.
Morgan had field goals of 28 and 38 yards around a 46-yard field goal from Nebraska's Pat Smith that left the Nebraska lead at 10-9 at halftime.
Nebraska's Ameer Abdullah, who rushed 27 times for 122 yards, opened the second half scoring with a 1-yard run. Morgan added a fourth field goal midway through the third period not long before the record-tying 99-yard play between Armstrong and Enunwa.
The formal name of the game is the Taxslayer.com Gator Bowl.