Stripper clips and speed loaders currently function as magazines and stay attached to the ammo/weapon.
Their function in real life is to allow for a faster reload. You empty the clip/speed loader into the weapon. After reloading you are left with an empty clip or speed loader.
SKS clip reload
https://www.youtube.com/watch?v=o9V8qhMzwr4#t=34
Mosin clip reload
https://www.youtube.com/watch?v=tLoo6bA1eAU
revolver speed loader
https://www.youtube.com/watch?v=BOgu4yJAWoI
shotgun speed loader
https://www.youtube.com/watch?v=pIIFiY-iQhU
Hickok45 magazine vs clip (featuring the SKS)
https://www.youtube.com/watch?v=UoSNHe413rY
In the video he points out that the clips for the M1 Garand actually go into the weapon, an exception.