The most important of these is the breech plug. It is made to withstand 100 grains of high quality BLACK POWDER lighting up and moving a bullet of 480 grains minimum and more likely 500 to 550 grains either lubricated or paper patched. The pressures that develop in long range rifles firing elongated bullets are higher by far than any round ball rifle.
Most breeches today are made for round ball barrels which work at far lower pressures than the muzzle loading match rifle. The breech must be designed in such a way so as to minimise pressure on the base of the nipple. Just because a barrel has a "patent breech" or bolster instead of a drum and nipple does NOT make it completely suitable for a muzzle loader firing a long, heavy projectile. The breech MUST BE DESIGNED with this application in mind.
Pictured right is an original Whitworth match rifle designed for long range target shooting.