440 Cor-Bon Ammo for a Desert Eagle

[Varyon]

It should be pi+, as it's 10.89mm (which IIRC is fairly low on the pi+ scale). The increased penetration would be on account of it going faster than most .44 caliber projectiles (and sufficiently-so as to have superior penetration to the .50 AE... or at least that was the goal).

For a quick back-of-the-envelope calculation, GURPS damage is roughly linear with velocity if mass and cross-section remain constant. Wikipedia gives two very different velocities for 240 grain .44 Magnum - 1180 ft/s vs 1475 ft/s - and I'm not certain which is more typical. A 240 grain .440 Cor-Bon has a velocity of 1800 ft/s. That's either +50% or +20% to damage, respectively. Note that would be relative to a .44 Magnum.

Less back-of-the-envelope, Douglas Cole previously worked out that average damage, in points, is typically around 0.6*SQRT(KE/cal^0.4), with caliber in mm and KE in J. Applying that here, you're looking at 18 points, which is right between 5d pi+ (average 17.5) and 5d+1 pi+ (average 18.5).