Muzzleloading rifles are black powder guns. That cannot be stated enough. Too many people have died because they put the wrong powder into the muzzle of their rifles. Please make sure that you are only using black powder! Having stated the words of caution there are basically two methods of loading a blackpowder rifle. Loose powder and Pyrodex pellets.
Loose powder allows for exact measuring to produce a very accurate load. While many .50 caliber rifles are capable of shooting up to 150 grains of powder, it often is not necessary. Pyrodex pellets are preloaded 50 grain pelletized blackpowder charges. These make reloading fast, and accurate. By dropping two or three pellets into your barrel, all that is needed is to seat the bullet and you are ready.
Powder on the other hand allows for precise loads. Hovey Smith, a well-known author and expert in all things blackpowder once offered this advice when discussing introducing people to the joy of shooting blackpowder. “Load it light, very light to get used to the gun.” Smith said. Elaborating by saying that there is no rule that you have to put, 100 or even 150 grains into a rifle to shoot it. “I often load only 50 grains when testing a rifle for the first time.” There is less recoil, less blast and a lot more fun to shoot.
Some hunters who also enjoy reloading rifle bullets will find the powder is more precise. I have some friends who use a variety of charges for their hunting purposes. One will load his .50 CVA with 120 grains of powder when hunting whitetails. Another uses 95 grains while a third chooses to use 130 grains. These precise loads are not possible with pelletized Pyrodex. Having said this, for beginners, not having to measure loads can be advantageous. There is less room for error when all you have to do is count pellets.
Time at the range is the best method to choosing the best load for you and your hunting style. In a .50 caliber rifle, one hundred grains of powder is sufficient at modest ranges. Less is even ok if you are limiting your shots to under 75 yards. Using a moderately weighted bullet and shooting at modest ranges does not require a heavy load of powder. Personal preference is to load as light as possible. There is no need to punish yourself for over loading a rifle. Determine a load that works for you and your hunting style, for most applications here in the south, a modest load around 100 grains will suffice when using a quality bullet.
Test both powders and pellets, with different bullet weights and configurations and you will quickly determine a load that will meet your needs when you enter the woods.