Lehner said the weapons will be in combat within days, before the end of the month, though he declined to reveal exactly where they would be used.
The U.S. military plans to order 12,500 XM-25s at a cost of $25,000 to $35,000 each. The rounds, about the size of a roll of quarters, cost between $25 and $35 each. Though the initial plan is to put an XM-25 with each squad and Special Forces team, the combat assessment, he said, will help gauge whether the military needs to order more, which will drive the price down.
Dan Goure, vice president of the Arlington, Va.- based think tank, the Lexington Institute, said the XM-25 goes a long way toward correcting what he sees as major deficiencies in military operations. But, he said, the Army needs to reach a bit farther.
While the Department of Defense has sunk large sums of money into tanks and vehicle-mounted weaponry, the "dismounted warrior" was left largely exposed, a "huge" problem in a place like Afghanistan where soldiers are charged with hiking into dense hillsides where no vehicle could ever travel.
"What we had not spent a lot of time working on was the equipment, personal equipment, guns and weapons for the dismounted soldiers," he said.
The XM-25, he said, is a good upgrade, though he stopped short of agreeing with Lehner's "game changer" assessment.
Goure, who served on the 2001 Department of Defense transition team, praised the ability of the weapon to be useful both in urban settings and caves.
"The nice thing about it is I don't have to carry two or three different weapons or two or three different shells," Goure said. "It's certainly an important step forward because it provides much heavier firepower to the dismounted squad and that's hugely important."
But he questioned whether the rounds were high-powered enough, opining that the small rounds may have limited explosive capacity.
"Is it going to be enough or do you need still a heavier duty" weapon? he asked. "You'd like something that might be a bit longer-range, a bit heavier in explosive power."
"Short of that," he said, "it is pretty good."
Development of the XM-25 has been about 10 years in the making. It first was fired on a test range on Aug. 11, 2009.
The guns also have made an appearance in video simulators to train soldiers and even online games for civilians, including "America's Army."
Lehner, who penned an article on the weapon titled, "Nowhere to Hide," said he's confident it's the only weapon of its kind.
Through a lot of "war gaming," he said, the United States knows other militaries are working on high explosive airburst technology, but are "years behind."
"We have to stay ahead of the technology curve," he said. "If we don't, someone's going to get ahead of us."
But eventually, they will catch up, Lehner acknowledged. And then the Army will start all over again.
"You cannot prevent enemy forces from developing whatever they're going to develop," he said. "Sooner or later, they're going to get it, so maybe you should have it first."