Oleg,
signs of headspace problems may include a slightly brighter or shiny ring around the case rather than an obvious bulge, or loose primers as the most obvious. Having a smith check it, esp. on any older mil.surp. firearm is highly recommended.
Master Blaster,
Headspace to say it as simple as I can, is the amount of space in the chamber (from the breechface forward)for the cartridge to fit, usually only about .005". This space is necessary because if the cartridge was exactly the same size as the chamber, it would cause extremely difficult extraction of the fired case, and any irregularities in the ammo would not allow it to chamber. It is measured in different ways for different cartridges, (straight, bottlenecked, rimmed, rebated, belted, etc.) but always from the breechface to one of the following: the front of the rim, the datum line (a design reference) on the shoulder, the case mouth, etc., as the design of the cartridge calls for. Excess headspace can cause problems from stretching and weakening the case, sometimes causing blown primers, or case head seperation, and can be dangerous as hot gasses may come back toward the shooter.
hope this helps
Bergie
edit-add
wow, a couple of good answers real quick while I was trying to post and yell at the kids at the same time
[This message has been edited by bergie (edited March 24, 2000).]
[This message has been edited by bergie (edited March 24, 2000).]