The campaign, called "Fry Day," offered an order of small fries for free to introduce a crispier fry, which holds its crunch longer than their old fries, Murray said.
In less than four hours, the Dual Highway store sold about 1,500 small fries. Murray expected to sell 2,500 by the end of the day - about 1,800 pounds of potatoes, compared with the 360 pounds in a typical day.
But whether customers prefer their fries to those from McDonald's - as Burger King's commercials claim - remains to be seen.
"They do taste better," said Sean King, 7, of Hagerstown.
"More crispier," chimed in Sean's 8-year-old brother, John.
But their grandfather wasn't convinced.
"They're pretty good, but I would need McDonald's fries here too to make a comparison," said Mike Fletchinger, also of Hagerstown. "I like McDonald's fries, but these are pretty good."
Craig Conroy, a consumer analyst in Gibsonia, Pa. and author of "29 Ways to Improve Your Business," said the free fries for a day was a brilliant marketing ploy - customers taking advantage of free fries will likely buy a burger or shake, too.
"Everybody's been buying," Murray confirmed. "So far, we really haven't handed anybody just the fries."
And the timing was perfect: Fast food sales dip after the holidays, Conroy said.
"I think it's probably one of the biggest promotions in the history of the world," Conroy said. "You can't beat free Fry Day on Friday - it's a killer idea."
Though Conroy can't predict how much Fry Day will increase Burger King's sales - or if it's a step toward toppling McDonald's reign - it will likely increase their market share.
"How can you beat free? This is an excellent promotion. It couldn't be better," Conroy said. "It's obviously created a ton of free publicity for them around the country if not around the globe. I can't see how it won't increase their market share."
Laurel Dearhart, store manager at Burger King on 1066 Lincoln Way East, Chambersburg, Pa., also saw sales soar.
Though she didn't have an estimate on the volume of fries sold Friday, she said the store is doing well - probably beating sales at McDonald's.
"We beat them every day," Dearhart said with a laugh.
Mark Levin, owner of the seven McDonald's restaurants in Washington County, said he isn't concerned with Burger King's promotion and feels no need to compete.
"We don't have to. We have the world's best fries. Always have and always will be," Levine said. "I would be surprised if after today there's much talking about the new fry. I think the fanfare of their new fry is going to be short lived."