A breech-loading weapon, usually a gun or cannon, is one where the bullet or shell is inserted, loaded, into the gun at the rear of the barrel, the breech; the opposite of muzzle-loading. All modern mass production guns are breech loading.

The main advantage of breech_loading is a reduction in reloading time; it is much quicker to load the projectile and charge in at the breech than to force them down a long tube, especially when the tube has the spiral ridges from rifling.

Matchlocks were the first effective long guns, and the first to have breech_loading. The entire firing chamber was removable, to be reloaded or replaced. The chamber was held for firing by either wedging or screws. There were numerous problems, one of which was seemingly insoluble _ fouling and pitting at the join between chamber and barrel leading to increasingly more severe windage and backflash _ a flare of gunpowder through the join. There were many attempts to solve this, attempts that continued through the development of the wheellock and the flintlock. All failed to completely seal the breech and compared to muzzle-loaders they were much more expensive, more fragile and difficult to repair.

The improvements to breech-loading came with the general improvements in precision engineering and machining in the 19th century. The Austrian Crespi or the American Hall were improvements, but still weak. The caplock breech-loader was a clear improvement through better manufacture and better metallurgy. It needed the development of the metallic cartridge to allow successful breech_loading. The gun barrel could now seal against an expanding cartridge with the detonation forward of the join rather than behind it.

The low_powered copper Flobert cartridge was invented in 1836, as was the pinfire cartridge (Lefaucheux), although this required fixative work by Houiller in 1846 to produce a workable cartridge. Rimfire cartridge (1850s). Centrefire cartridge (Pottet, 1857. Berdan or Boxer priming). See Cartridge.

The first widely used breech_loader was the Prussian Dreyse Zundnadelgewehr or needle-gun, a bolt action single-shot rifle invented in 1838 and so called because of its 0.5-inch needle-like firing pin which passed through the cartridge case to impact a percussion cap at the bullet base. The cartridge was actually paper and the gun had numerous deficiencies but the great successes of the Prussian army, convinced many other nations to quickly develop their own versions. The French adopted the new Chassepot rifle. The British initially took the existing Enfield and fitted it with a Snider breech action (solid block, hinged parallel to the barrel) and firing the Boxer cartridge. Following a competitive examination of 104 guns in 1866 they adopted the Martini_Henry lock with trap_door loading. In the USA the enormous number of war surplus muzzle_loaders produced the Allin conversion Springfield in 1866, with a trap_door loading mechanism of the British gun, the firing mechanism was very similar to the Prussian gun. The development of the tubular magazine rifle in the 1870s rendered all these obsolete.