Windfall,
The cross-section of almost all expanding bullets is a "football" near the entrance hole, with the rest of the wound channel a lot smaller--though exactly how small depends on the expanded frontal area of the bullet. I don't know of ANY expanding bullet that creates a "cone-shaped" wound channel.
For your wishes one of several bonded bullets would tend to produce a bigger exit hole, such as the Norma Oryx, Swift A-Frame or Scirocco II, Trophy Bonded Tipped, Woodleigh Weldcore or even the Nosler AccuBond. All tend to result in a wider mushroom than the Partition. The downside is the wider mushroom causes them to stop under the hide on the far side more often, which of course doesn't result in a wider exit hole!
When I want to make sure a deer doesn't run far in thicker woods (or down into nasty canyons) I shoot 'em through the shoulders and spine, not the lungs. Holding directly in line with the front legs, about 2/3 to 3/4 of the way up the body, does the trick. In fact my wife shot her biggest-bodied whitetail buck (and she's shot quite a few) that way, because it was almost the end of legal light, and she was hunting a thick riverbottom. The buck dropped right there, the bullet a 100-grain Nosler Partition shot from her .243 Winchester--which exited.
