Man am I glad I found this thread. I've been using .50 caliber PowerBelt 295gr bullets, with 100gr Triple7 pellets out of my CVA Optima Pro 209. Every deer that I've shot with that combination has dropped within 30 feet of where I shot it. I have NEVER had a pass-through with a PowerBelt, so I'm glad that they dropped close by.
Every deer that I've shot with a PowerBelt has looked like a blender had been used on it's internal organs. I also have to be very careful when field dressing them because there are always sharp jagged pieces of bullet inside the carcass that will cut upon contact.
My problem with the PowerBelts is simply that at ranges over 100yds my shot groupings start to really wander around, and that's shooting off of a rest at the range. For a long time I thought it was just my shooting. However, after trying different bullets I figured out that the PowerBelt was destabilizing in flight.
Fortunately, where I hunt, it would be rare to be able to see or shoot at a deer 100 yards away because there is so much foliage. 99.9% of shots I take are going to be 60 yds and under (mostly under), and the groups are fine for that range.