...FILL .303 STRIPPER CLIPS
Unlike later model military rifles, the Lee Enfield magazine was not intended to be removed when empty and replaced with a full one. Lee Enfields were to be loaded with 5 round chargers (stripper clips), or topped-off from the breech with loose rounds. The rifle was only issued with one magazine. Because .303 ammunition has a rimmed case it is common to experience feed jams if the clips are not loaded properly. The rims of the middle and the end cartridges in a correctly filled clip should be behind the rims of the other 2 rounds as shown in the illustrations below. The cartridges should be pushed from the clip into the magazine with one strong steady motion of the thumb. After emptying the first clip, it is removed by hand. The second clip is ejected automatically when the bolt is shoved forward.
There will be occasional jams due to rim overlap even when clips are correctly filled but they will be minimized.