I am not totally against powerbelts, I think they are fine for mulies and whitetails. What bothers me about powerbelts is my hunting partner and I had one really good experience with powerbelts, and so we felt very confident using them. Because of that confidence we kept using them and we had many bad seasons before I finally wised up and switched. I apologize for such a long story, but my field experience with powerbelts goes back about to 2006.
2006: The first year my hunting partner got a muzzy tag he dropped a really nice 6x6 in its tracks at like 150 yards. I consider this too far of a shot, but the elk drops with a 348 grain areotip powerbelt, and 85 grains of 777. We both looked at each other, and were like that was easy. The bullet was perfectly mushroomed on the far side just under the hide. Both of us were then feeling really confident about hunting with a muzzy and the powerbelts. I thought man is muzzy hunting easy, the season is in September so you get to hunt the rut, how can this get any better. Two days later he loses a bear at just under 100 yards, no blood, nothing. Thought that was weird, the blood was probably absorbed in the bear hair, and it was a fluke that bear was not dead.
2007: Where we hunt you 100% get the muzzy tag with 1 pt, but you can sometimes get the tag without a pt. So I get a deer tag and an elk tag. I shot a mulie that took two shots I was hunt with 338 grain platnium aerotips and 85 grains of 777. My bullet punched right through broadside at about 50 yards on the first shot, hardly any blood, the deer runs a big circle and stands behind a tree about 100 yards away, and the second shot hardly penetrated and looked like you crushed it with a sledge hammer. I did not see any elk worth shooting that season.
2008: Still feeling pretty confident with the powerbelts and 777. My friend gets the elk tag. We video tape the hunt, at 80 yards shooting a really nice 6x6 it was slightly quartering to good shot placement, the elk looks wobbly but runs at us, then spins around and runs away. We were thinking the thing is going to drop, and should be lying in the oak brush. We go up to the spot, and no blood. Look all around, search everywhere and nothing. We look for a few days, and keep glassing the area looking for magpies, we never find anything. You can see the body ripple and the shot placement in the video and we never find that elk, or any sign that he even hit him.
A few days later we keep hunting, and he shoots a big 5x5 just before dark, under 100 yards. We can't find him that night, the next day we go out, find the 5x5 with cows, and he has a limp. It takes like 3 more shots to get him down.
In 2008 and 2009 I hunted 1st season so I didn't have any muzzy mishaps.
2009: My friend again draws the muzzy tag, I hunted the first weekend with him, and we see a couple small bulls but nothing worth going after. I don't have enough vacation to take off the week, so I go back to work. Later in the week, he puts a stalk on a big 6x6 gets within 75 yards shoots broadside and the thing runs off very little blood, and he never finds it. Later in the week, he finds the bull bugling its head off chasing cows, so he thinks he grazed it or something. A few days later he shoots a 6x7 at 100 yards, and it took every speed loader he had, he said he shot him 7 times, and just kept shooting until the bull dropped. After that he swears off muzzleloader and will never again chase elk with a muzzy. I start to think, maybe he is a bad shot, and that wouldn't have happened to me so I keep putting in for the tag, even though I was with him and witnessed some of the hunts and the shot placement.
2010: So I am still feeling good because I have never lost anything with my muzzy. So I put in for the tag, and draw it. I chased a nice 6x6 for most of the season, and had some close calls. On the last day, I get 125 yards away broadside, I shot, and the elk is all wobbly looking, and I am waiting for him to drop. Now looking back at it, I am kicking myself, for not reloading and keep throwing powerbelts at him. He walks off in the brush, and I am confident he is laying down to die. We give it some time, and I go up to where he was, and there is a decent spot of blood where he was standing. I follow the blood trail for a little bit, and then it drys up. I hunt the draw I think the bull went into, and don't find him. The season ends, and I don't get an elk. A few days later, we find the bull chasing cows, acting like he was never shot. After that experience I gave up powerbelts, but was determined to get an elk with my muzzy.
2011: I get the tag again. I switch to 300 grain Thors, and BH209. It seemed to shoot about the same, but I had to switch out my breech plug in order to shoot the BH209. I upped my load to 90 grains of BH209. I shot a mulie at 100 yards on the 1st weekend that dropped in its tracks, I found the Thor on the far side just inside the hide, and it opened very nicely just as advertised. I hunted the elk the rest of the week, and ended up shooting a 5 x 6. The first shot was about 60 yards straight on. I learned my lesson, and kept reloading and shooting until the bull was dead. Although he did not drop, there was a blood trail unlike the powerbelts and it had chunks of bone in it so there was some serious damage to the elk. And best of all I found my bull.
Elk are extremely tough, especially when they are all rutted up in Sept during the muzzy season. Plus you are using open sights so it's more challenging. I believe elk shot in the rut can take a licking and keep going, even more than normal because they are all full of adrenaline and hormones. This is just my experience, and I am sure tons of people will give you great reviews on powerbelts. I am not sold on BH209 because I am not crazy about the new breech plug I have to use in order to shoot it. I feel confident I could use 777 or BH209, but I will definitely not be using powerbelts.