A musket is an unrifled longarm, usually of a larger caliber than rifled arms. Muskets are commonly found in .65-.70 caliber, while rifles are generally found from about .30 through .58 caliber. Muskets can also be loaded with shot and used as fowling devices. The musket ball fits loosely in the bore, thus making combat loading more rapid than the tighter fitting patch and ball combination used with a rifle. Even though the musket had limited accurate range, its speed made it the choice military weapon until the widespread availability of cartridge arms.
A muzzleloader is any arm, rifle, pistol, musket, etc. that is loaded from the muzzle end.
A flintlock is a weapon using a piece of flint hitting steel to create sparks that set off a small charge of priming powder and cause ignition of the main charge in the barrel. Contrary to popular belief, it is not fire from the priming charge that sets off the main charge, but the heated gases coming from the priming charge. Percussion muzzleloaders are fired by the hammer striking a percussion cap (similar to a modern primer) which sends a jet of fire down a nipple into the main charge. As a result, percussion guns are far more dependable, but were often not commonly accepted on the frontier due to the fact that you needed to carry a supply of caps. Many backwoodsmen continued to carry flintlock weapons for many decades following the general availability of percussion arms. The term "flash in the pan" refers to the situation where the priming charge of a flintlock would ignite but fail to fire the weapon.
A blackpowder rifle is most commonly a muzzleloading weapon, but also includes cartridge weapons loaded with black powder.
Other terms commonly used to describe black powder muzzleloaders are "smoke pole" and "front stuffer".