[TranterUK]

I know this will be old hat to many, but not everyone will know about it.

If you use an semi automatic pistol or rifle, consider numbering your magazines on the base.

Many will go to the range with a few mags and while there may have some jams or feed problems. Others might not seat properly, failing to lock in place without a fiddle. By numbering the mags you will know if any in particular give you problems. If it's used for defence, you know which mags not to use.

Whenever I had a magazine that gave repeated problems I used to bin it. Other options are to paint the base red and use it for mag change practice, some determined souls even used to fill them about a third with lead, to replicate the weight loaded.