Also, the energy contained in the cartridge will now have to do double duty, in that it has to extract/eject the fired case, but it also now has to "extract" the next round from the magazine.
Huh?
What the heck do you think extracts the next round in a conventional pistol?
When you pistol only has 2.9 inches of barrel length, an addtional 1.2 inches IS A BIG DEAL.