I can honestly say a PRB would be the very last thing I would want to gut shoot a deer with! EVER!
A couple of years ago I was centerfire hunting before I got back into muzzleloading again. I had a very nice,20" wide 11 point come in front of me at about 45-50 yards away. Being told to bring something that will deal with some brush I took my 416 Rem Mag loaded with 300gr Barnes X-Bullets. I waited for the deer to clear a 4" striped maple tree, one more step was all I needed. He took two. The shot actually knocked him down, he wallowed around for a split second and regained his footing and took off, before I could get another round in him. I knew the shot had connected so I waited about 35 minutes and ate lunch. I walked down to where I had shot him, and the first thing I noticed was the smell. That smell every hunter hates. I was lucky enough to find a sparce blood trail that got better and better. The deer had only went about 150 yards before piling up. Squarely hit through the stomach. If I hadn't been using that large of a caliber this post would probably be about a great buck that got away. Field dressing the deer I found that even though the bullet had passed straight through the stomach without touching a bone, it had enough shock to actually tear the liver almost in two. I know I was very lucky.