The Army has half a million M4 carbines, the lightweight version of the Vietnam-vintage M16. So if the service was going to invest in a replacement, it wanted a “leap ahead” that would, among other things, cut in half the number of times the weapon jammed – a criterion the Army has not made clear until today. None of the eight designs offered for the Individual Carbine competition met that standard, Army officials said, so the service is going to stick with the M4 indefinitely.

That, in a nutshell, is the word from a half-dozen Army experts and officials at a hastily convened press conference to explain the service’s decision to, for all practical purposes, kill off the $1.8 billion Individual Carbine program. The Senate Armed Services Committee has already cut the $49.5 million requested for the program in 2014 “based upon the Army’s decision not to continue with the competitive evaluation program,” to quote the SASC’s official summary of the bill, released just before 1:00 pm today. On the flip side, the Senate left in $21.3 million to buy 12,000 more of the current M4A1. But after years of technical controversy and political pressure, M4 critics are unlikely to just let the matter rest.

“There was no capability-based assessment justification, no requirement,” said one skeptical Congressional staffer. “A lot of money and time has been spent.” Stopping the Individual Carbine now, the staffer said, “makes sense if nothing gives us a leap ahead in capability – but no doubt the politics will continue to churn.”

Certainly the Army wants to close the door on the Individual Carbine. “I want to be very clear: none of the vendors met the minimum requirements,” said Brig. Gen. Paul Ostrowski, the chief of Program Executive Office (PEO) Soldier, which oversees all the individual equipment carried by G.I.s. “If the army could have moved forward in any way, shape, or form, we would have. We are surprised by these findings.”

Ostrowski emphasized: “The Army is not cancelling the IC competition, the Army is the position where it must conclude the IC competition.”

That may sound like a distinction without a difference. Legally, however, there’s all the different in the world, especially since there is legislative language in the House Armed Services Committee version of the annual defense bill saying “The Secretary of the Army may not cancel the individual carbine” (emphasis mine). Even though the statute, the National Defense Authorization Act for fiscal year 2014, is months from final passing into law, the Army doesn’t want to flout the will of Congress too directly.

It is Congress that has forced the Individual Carbine program on an unwilling Army.  The pressure has come from both chambers and both parties. House Armed Services Committee’s top Democrat, California’s Loretta Sanchez, put the “may not cancel” language into the NDAA during mark-up two weeks ago. But the fiercest proponent of a new carbine has been Republican Sen. Tom Coburn of Oklahoma. (Click here for Coburn’s case against the M4 in brief). Coburn has been pressuring the Pentagon to test M4 alternatives since at least 2007 and has twice used his Senatorial prerogative to put administration nominations on “hold” as a means to pressure the Army. (The first hold was on Army Secretary Peter Geren in 2007, the second was just last fall on Army acquisition chief Heidi Shyu). We’re working to get comment from Sen. Coburn and Rep. Sanchez, but they can’t be happy.

The M16 rifle and its M4 carbine variant have come in for bitter criticism since the M16 was introduced during Vietnam, where the gun’s innovative but finicky mechanisms kept jamming because conscript soldiers failed to keep it properly clean in the muddy conditions of Southeast Asia. Even today, there is a bitter debate over whether the “direct impingement” gas-operated recoil system lets in sand and dust to jam the weapon in Afghanistan.

There’s a whole separate debate about the killing power of the M16/M4 family’s relatively lightweight 5.56 millimeter rounds, but the two controversies converged after the Army issued a new, more lethal bullet in 2010, the M855A1 “enhanced  performance round,”  which critics almost immediately accused of fouling the gun barrel.

“We do extensive post-combat surveys after every unit redeploys from theater,” said Brig. Gen. Ostrowski. “Over the past four years, the survey results have revealed that in compilation over 80 percent of the soldiers are completely satisfied with the M4… and that trend is moving upward [to] 86 percent.” As for the new round, he said, “we have experienced absolutely zero issues with the M855A1 in combat.”

“I had heard that anecdotal information that the M855A1 did create more fouling,” added the Army’s project manager for ammunition, Col. Paul Hill. But when he arranged an extensive series of tests, Hill said, “we found…. there was no significant difference in fouling between the M855 [the old round] and the M855A1.”

One source close to industry, however, told me that “several of the manufacturers had severe degradation to their barrels using the new ammo” when they tested their Individual Carbine contenders.

Originally the Army had told the companies their offerings would be test-fired using the old M855. When the M855A1 became the official standard in 2010, however, the Army told the competitors they should now use the new round instead. The problem was that industry had limited access to the new ammo. What they got, they had to get from the Army, with dire warnings not to take even one round back from the Army-sanctioned test range.

The Army gave each company 10,800 rounds of M855A1 to test-fire before the official competition began, so they could work out any kinks in their designs. That may sound like a lot, but the Army required that each competing weapon be able fire 3,592 rounds, on average, before jamming. 10,800 divided by 3,592 equals three. That means each company had enough bullets for, at most, three test runs to see if its weapon met the Army’s standard before submitting it for consideration. In the actual competition, when each gun fired 25,600 rounds, all of them failed.

That said, the current M4A1 carbine doesn’t meet the standard of 3,592 “mean rounds before stoppage” (MRBS), either. After about ten minutes of relentless badgering by Army Times reporter Lance Bacon and myself, the Army finally said how well the current standard-issue weapon did with the current standard-issue round. “I’ve got the data in front of me now,” said Col. Hill, after an unnamed assistant dug up the figures and slipped them in front of him: During testing in 2010, M4A1s loaded with the M855A1 round fired, on average, 1,691 times before jamming.

So the 3,591 mean rounds between stoppage the Army wanted for the Individual Carbine was 112 percent better than what the M4A1 can currently manage. That would definitely be a “leap ahead” in reliability. How far short of that standard each competitor fell is proprietary information the Army could not disclose. But the service argues that anything less than a 112 percent improvement wouldn’t justify the huge investment required to issue everyone new guns.

“The IC competition was based on [getting a much greater capability than the M4A1, otherwise we would not have gone out and done a competition,” said Brig. Gen. Ostrowski. “We wanted something that was challenging but achievable [for] industry and we thought we could get there. This is a surprise to all of us.”

Each competitor “had a different reason why their weapons failed,” Ostrowski added. Neither the Army nor the industry has yet done all the forensics, he said: “It would be premature for us to tell you exactly what the issue was.”

The problem is that, despite five years of back and forth between government and industry, the gunmakers apparently still did not have a clear idea of what the Army actually wanted.

“If the Army wants something really new and different, you’ve got to get real specific real soon in that process,” said Allen Youngman, the retired Army two-star who heads the Defense Small Arms Advisory Council, a trade group. Instead, industry sources say, the formal solicitation looked like the Army wanted a modestly improved M4A1.

Between the death of the Improved Carbine this week and the cancellation of the XM8 rifle in 2005, Youngman told me yesterday, “if there is a need somewhere in the Army for a new capability, we apparently missed the last two opportunities to communicate that fact to industry.”

So maybe gunmakers could have delivered something markedly superior to the current Army carbine. Maybe they couldn’t have. But the Individual Carbine competition does not seem to have settled the question decisively one way or the other.