Blank rounds are regularly used on training exercises and great care is taken to ensure that live rounds are not accidentally mixed up as this could have potentially fatal results. With the best will in the world, however, mix ups can occur and one of the ways the British Army tries to make things safer is to have dedicated magazines for its SA80 rifles that are specifically for blank rounds:
The most obvious external feature of these magazines are the vertical yellow stripes that clearly show that these are blank rounds. If a soldier has a magazine that is not yellow striped it can be clearly seen and investigated. The magazines themselves are designed so that live rounds cannot fit inside them, thus ensuring they are only ever loaded with blank rounds. This can be seen with the vertical tab and the different floor plate of the magazine:
To help distinguish the magazines in the dark, when the yellow stripes cannot be seen, a plastic tab is fixed to the magazine to give a tactile indicator that this is a blank, not a live magazine:
Like any other magazine, these blank magazines need to be cleaned and maintained, so the base of the magazine can be removed to allow the spring and floor plate to be removed to be cleaned and lubricated:
These magazines are used in combination with the blank firing adaptor that can stop up to three live rounds to help reduce the risk of a live round accidentally being fired during training exercises. It is not fool proof of course (human error is always a factor) but does make it much more unlikely that a serious accident will occur.