A tube magazine is most commonly a fixed magazine that takes the form of a cylinder under the barrel and stores ammunition for rifles and shotguns.

Though the design varies from maker to maker there is always a spring and a follower which pushes the ammo towards the feeding ramp or lifter for subsequent loading and firing.

Because the cartridges are positioned end to end, the bullet design on cartridges for use with tube mags have to be some sort of round nose, flat point, or hollowpoint as a pointy point can cause the cartridge ahead of it to discharge if it hits it with enough force, like for example if the rifle is dropped. For those who are not familiar, the primer is at the bottom of the cartridge, the primer is quite sensitive and can go off with the slightest dent. A cartridge firing outside the chamber can be catastrophic for the firearm and anybody close by.