New Army "Caliber Configuration Study"

[Tony Williams]

Let's see 39mm to 43mm is a 10% increase in capacity.

If you look carefully at the photo you'll see that there is a bigger difference in the case capacity than that, because the neck is shorter. The main body of the case is around 25-30% longer. The increase in propellant wouldn't be as great as that because of bullet intrusion, but it should still be significantly more than 10%.