The .50 caliber is a little bigger then the .45 caliber in diameter. The .50 caliber is 1/2 inch across. They would use the same powder charge to fire their respective bullets. The .45 caliber shoots a lighter weight projectile then the .50 caliber. Due to the weight difference the .45 caliber projectile will be faster, but will also have less energy at longer ranges. I personally want as much lead as I can get to enter and expand in my target. Bigger hole theory if you know what I mean.
The 209 primer is the same thing that shoots off a shotgun shell. The #11 cap is a much smaller cap. The 209 primer throws more heat into the powder charge and therefore they claim a better ignition. I have shot the Knight Wolverine with #11 caps and never saw an ignition problem yet. They also make a conversion for the Knight to change it over to 209 primers, but I just do not see the need for it.
If all your shots are going to be 150-200 yards, then you might get some advantage out of the extra two inches of barrel length, but really I think the fact that the Knight has a Green Mountain barrel will more then make up the difference of the two inches. In all the years I have hunted I have never shot further then 90 yards at anything with a muzzleloader.
You can shoot Pyrodex Pellets, Triple Se7en pellets, or loose powder. You can also shoot my favorite, black powder. Loose powders are cheaper to shoot. I also feel you can tune your rifle better but there are a lot of shooters out there happy with pellets. I have only shot pellets twice, and they were not my pellets....
The Hunter Bolt has a 24 inch barrel which is the same as my Staghorn. It has trouble burning more then 120 grains of FFg powder. So there is really no need for three pellets. You might get some 30 grain pellets and then make you loads that way. What any of these people here will tell you is, 100 grains of powder is plenty of power. Loose powder recommendations are 100 grains.
The Wolverine has a max charge of 120 grains of powder whether it is in pellet form or loose. I have been experimenting shooting FFFg powder which is for light caliber rifles and pistols out of the Wolverine and it is working really good. 90 grains of FFFg powder really packs a punch.I also think the Knight has better balance and does not jump in recoil as bad as my Staghorn. I have no scopes on them, but the Knight is a smooth shooter.
If all you want to shoot are powerbelts, then you might like the CVA better. I would still get a .50 caliber and shoot the 295 grain or the 348 grain powerbelts. But at the ranges you are talking perhaps a .45 caliber is better. I have just heard that some .45 calibers are hard to tune and get a load working. By the way, powerbelts are expensive to shoot. They are almost a dollar each. So I hope the rifle tunes in fast and you do not want to practice too much. I have had good luck shooting REAL concials out of the .50 caliber CVA but only shot them out to 100 yards with the open sights.
I have never had to use the customer service from Natchez. I am sure they are good to deal with, just like Cabela's or Bass Pro. Only you can decide what rifle is best for you. Don't let the bigger .50 caliber scare you off. They have a better bullet selection for the most part and are much easier to find stuff for.
If I was trying to get by under $200.00 I personally would go with the .50 caliber Knight Wolverine II . I think it is a great rifle. I just got mine about a month ago and am still trying different loads in it. It seems to shoot about anything I shove down it, other then coinicals.
Both my CVA and Knight seem to need a fowling shot. Thats not a big problem. There are some excellent books out there to help you learn the sport. The Knight also comes with a video that teaches you how to load, shoot, and clean the rifle and some other stuff.
These message boards area great way to get information. Any question you have, just ask away. People here are more then happy to help you and answer any question you might have.
Good luck on your choice.