Brandy, there is a HUGE difference between a 400 Whelen or 44 Magnum and a 45 ACP. They are night and day. The only way you will get a 45 ACP to reliably penetrate through both lungs of an ELK is to use FMJ, which will leave a marginal wound. Round nose bullets that don't expand don't cause much damage. Muscle tissue stretches around the wound and almost completely closes back up. Semi-auto handgun rounds simply don't shoot projectiles that are appropriate for Elk.
Did you miss that Mauser is using a 1911? Good luck getting a HC bullet with a nice big flat meplat to load through a semi-auto. Some SWCs will work in a 1911 but they usually have more of a rounded profile. I said it in my post. The minimum for Elk in handguns is 44 Magnum. I have no doubt the 44 Magnum or 45 LC can kill an Elk. We are talking about a 45 ACP here. Not a Magnum revolver cartridge. Just because they are similar in caliber does not make them the same. The 45 ACP launches a 230 gr bullet with diminutive sectional density at a paultry 850-950fps. That simply isn't enough to get the job done. I'm saying a 45ACP semi-auto has no place as a hunting firearm. Unless you are plinking and going after small game.
The only 45 ACP load that I can think would be somewhat effective on Big Game would be Buffalo Bore's 45 ACP +p 255 gr SWC load. It is rated at about 960fps. That would be about the minimum that I would use on an Elk in an emergency. I think somebody would have to be completely nuts to actually purposely hunt Elk with a 45 ACP semi-auto pistol.
We aren't just talking about killing an Elk. We are talking about killing one quickly and humanely. A 9mm pistol will kill an Elk. The question is when and where? Probably many hours after the shot and a couple miles away from where it was shot.