Many beginning black powder shooters find they are unable to achieve the accuracy they expect from their muzzleloading rifles. Here are some areas to check out.
Sights - Be sure they are firmly mounted, some factory sights have extreme movement of the rear sight blade as they come from the factory. Check the mounting screws. If the are loose, tighten them up. Be careful. Use the right size screw driver and do not over tighten and strip the threads.
Scopes - If you have a scope mounted on your rifle, make sure it is proper for a muzzleloading firearm, not just any airgun scope, crossbow scope, or small bore rifle scope. Be certain the mounts are solid and there is no scope movement.
Tip: Apply a small amount of clear silicone sealer to the scope rings before installing the scope. Tighten the scope rings enough to snug the scop, but not all the way. Wait 24 hrs., then finish tightening the scope. Your scope will be firmly mounted in its own perfectly fitted silicone sleeve. The excess sealer can be rubbed of with your finger or a toothpick.
Bullets - Match your bullet to your rifling. Since there is no one answer to the question "which bullet is best", try several different bullet types to find what's best for your particular rifle. As a rule of thumb, barrels with a 1 turn in 66" rifling will do best with round ball; 1 turn in 48", round ball or conical bullet; 1 turn in 38" or faster, conical bullet. When shooting a patched, round ball, you can change ball diameter and patch thickness. Tighter is usually more accurate; however, more difficult to load.
Tip: Round ball shooters. Remember that your patch material, thickness and lube are as important as the ball size. Keep trying combinations until you get the best accuracy. Watch for cut or burned patches. These denote a problem.
Powder - Adjust your powder charge. Within the limits of safety, you may find one charge more accurate than another. Check manufacturer recommendations, but in general, a well made and well maintained rifle should perform well with 80 to 100 gr. 2Fg black powder for hunting, 50 to 60 gr. for target shooting. Fire a series of 3-4 shot groups, doing everything the same except varying the powder charge 5 gr. per group to determine what charge works best for you. A 100 gr. powder charge may have a lot of knockdown power, but if your rifle does not shoot accurately with that charge, the knockdown power won't mean a thing.
Except when using "Black Canyon Powder", don't pack the powder charge heavily. The projectile must be seated on the powder charge, but you will get better accuracy and ignition if the powder is not hammered into a lump. Black Canyon Powder on the other hand, must be heavily compressed to work properly.
Cleaning - Always clean between shots. A damp patch swabbed through the bore will promote safety and accuracy.
Nipples - Check the size of the port in your nipple. Replace nipples that have been burned out.
Flints - Check the size shape of your flint. Make sure that your flint is held securely in a in the hammer jaws. Use a small piece of leather to pad the flint in the hammer. Check the position of the flint. Experiment with different positions, even turning the flint upside down. Look for a large quantity of sparks, placed in the center of the pan. If the sparks do not hit the center of the pan, then see a competent muzzle loading gun smith and have him help you adjust the hammer angle.
Patch/bullet lube - Pre-lubed patches or bullets held over from one season to the next may dry out if not properly stored, leaving no lubrication factor which in turn reduces accuracy and makes loading difficult. Replace or relube.