wogpotter said:Lee-Enfield magazines aren't "interchangeable" in the modern sense. However #4 & #5 magazines are the same magazine, but they do need fitting to the rifle individually. This is usually a question of adjusting the feed lips.
#1 (SMLE) magazines do not fit either #4, or #5 rifles & #4/#5 magazines do not fit #1 SMLE rifles.