[updated] WASHINGTON: The Army’s proposed Ground Combat Vehicle would offer less combat power, at a higher cost, than buying the German-made Puma already in production or even just upgrading the Army’s existing M2 Bradley, according to the Congressional Budget Office. CBO issued a report today assessing different alternatives to upgrade Army heavy brigades‘ infantry fighting vehicles (IFVs), tank-like war machines with tracks and turrets designed to carry troops into combat.

[Click here for the GCV contractors BAE and General Dynamics critiquing the CBO report]

The non-partisan CBO, Capitol Hill’s in-house thinktank, has slammed the Ground Combat Vehicle program before, but never this hard. The office’s analysts took the Army’s own criteria and created a grading system that scored different combat vehicles for effectiveness. Using a scoring scheme that prioritized protection above all, followed by firepower, mobility, and passenger capacity, in that order, the CBO rated the Puma highest, followed by a notional upgrade to the Bradley, followed in distant third place by the GCV. (The Israeli-built Namer came in fourth). Even under an alternative grading scheme that weighted all four criteria equally — putting much more emphasis on the capacity to carry troops — the 6-passenger Puma still edged out the 9-passenger GCV, largely because of its superior firepower.

Add in the cost and risk of developing a new vehicle, and the analysis swings even farther in favor of the Puma. Since the Germans already have the Puma in production — the vehicle entered Bundeswehr service in 2011 — there’s no untested technology to cause problems. And even after buying 25 percent more Pumas to make up for its smaller carrying capacity, the Army would spend half as much as to develop, test, and build the GCV, according to CBO’s estimate: $14.5 billion for 2,048 Pumas as opposed to $28.8 billion for 1,748 GCVs.

[Updated: But, as one alert reader pointed out, CBO isn’t counting the cost to add three more vehicle crewmen to every mechanized infantry platoon to drive the extra Pumas — at least 900 personnel Army-wide — nor the extra maintenance personnel to support five vehicles per platoon instead of four, nor the ripple effects of rejiggering facilities built to accommodate four vehicles to take five instead.]

There is room to argue with CBO’s scoring system. To start with, since the GCV does not yet exist, CBO grades the vehicle based on the Army’s 2010 “Design Concept After Trades”; the actual GCV might be better or worse. For example, CBO assumes the GCV will have only a 25 millimeter cannon, rather than the Puma’s 30 mm, but Army officials I spoke to were still hoping for the larger caliber.

Indeed, in the CBO’s scoring overall, the Puma’s big advantage over the other candidates is its firepower. (CBO scored Puma as slightly better protected than GCV but slightly less mobile). In particular, Puma scored high for its ability to kill tanks and other armored vehicles.

But the Army deliberately chose not to install an anti-tank missile launcher on the GCV: The US military already has far more ways to destroy enemy tanks — from the M1 Abrams’s 120 millimeter gun to the A-10’s 30 mm Gatling, from the shoulder-launched Javelin missile to the air-launched Hellfire — than there are enemy tanks left to destroy. In the post-Cold War world, the nightmare scenario isn’t a long-range battle with hordes of Soviet tanks on the plains of Germany, it’s a close-quarters slugfest with irregular fighters hiding in crowded cities, where anti-tank missiles are largely irrelevant. So the Army decided it could better spend its money on other things — although the GCV is being designed to be upgraded with a missile launcher if the Army changes its mind.

The Puma also mounts its massive firepower in an unmanned turret, remotely controlled from inside the vehicle. The Army considered such a design for GCV but ultimately decided it needed the gunner and vehicle commander riding inside the turret, as they do in the current Bradley and M1, able to look through the gunsights directly and clear jammed weapons if the automatic systems break down. A manned turret weighs and costs more than an unmanned one.

The Army has also insisted, over and over, that it needs the capability to carry nine foot soldiers in addition to the crew: Bradley can manage four to six — seven if they squeeze — and Puma can take six. But more passengers means a bigger vehicle, which means more cost, especially if you have to armor the whole thing to a high standard against everything from anti-tank rockets hitting the top to roadside bombs hitting from below. The Army still thinks it’s worth the price to deliver a full nine-man squad to the same place at the same time, instead of scattering teams over multiple vehicles; but at the prices CBO is quoting, just buying a larger number of Pumas to carry the same number of troops looks awfully attractive.

One major omission: CBO did not assign a numerical score to one of the Army’s most important considerations, the alternative vehicles’ ability to power new digital radios, command-and-control computers, and other military network hardware. The report does say “the Puma’s communications and networking capability would be less than that of the GCV or the upgraded Bradley IFV.”

On the other hand, there is at least one other factor CBO didn’t include in its scoring that actually would have hurt GCV more to include. The Ground Combat Vehicle, fully armored, would weigh 65 tons, says CBO. (CBO earlier estimated 64 to 70 tons). The Puma, with all its add-on armor, would weigh 47. Strategically, that lower weight, and the reduced gas consumption that comes with it, would make Puma much easier to deploy abroad and then keep supplied with fuel — crucial considerations as the Army pulls out of Afghanistan and tries to revive its capability to deploy rapidly to distant crises.

Updated 5:55 pm with reader comment.