They are loaded with a “stripper clip” into the weapons magazine.
https://m.youtube.com/watch?v=NtQvIOFMe-8&t=2s&pp=2AECkAIB
Most mil rifles from first 1/2-3/4 of 20th century do this (I have enfield, SKS that do it, and my M1A could until I scoped it but it does detachable mags too)
yep...thanx.