The correct answer to the original question is, "it depends." Original guns like the Winchester Models 1873 and 1892 depend on a specific cartridge length for proper feeding, since the carrier rising acts as the cutoff. If a round is too short, the next cartridge coming out of the magazine can move back until it contacts the cartridge on the carrier and the carrier cannot move upward. Some modern actions have a cartridge cutoff which acts on the cartridge rim and will work with varying cartridge lengths.
The issue of pointed bullets in a tubular magazine is sometimes misunderstood by those who do not realize what really happens. If the magazine is full, or down to one round, there is no problem. But if the magazine has several rounds in it, and the recoil is heavy, the cartridges will move forward in the magazine under recoil, compressing the magazine spring. When the recoil stops, the cartridges will slam backward, driven by the magazine spring. If, at the same time, recoil has caused a rear cartridge to jump so that the bullet point is in the center of the magazine tube, the primer of the front cartridge can be fired by the bullet point.
Jim