Well, the name came from the fact that the firing pin (or sriker, actually) was a long, thin needle.
The cartridge was sort of egg shaped, with the bullet in front, a large wad of gunpowder behind it, and the entire thing was wrapped in a stiff paper.
The primer was actually in the base of the bullet.
In operation, the bolt was opened, the cartridge inserted into the chamber, and the bolt closed.
When the trigger was pulled, the "needle" would actually pierce the back of the cartridge, go through the powder, and strike the primer in the base of the bullet.
IIRC, the needle had to penetrate about 1.5" of powder to reach the primer.
The needle was the weak link in the operation. It had to be fairly thin, which meant that after a few shots the hot powder flame would seriously erode it and it stood a greater and greater chance of breaking in use.
I believe that there was a spare needle packaged in every 10 pack of cartridges, and soldiers routinely carried several spare needles in addition to what they got with the ammo.
They were designed for military usage, and they were one of the, if not the first, successful bolt-type firearms.
