What causes two cartridges to be released from the magazine? The top one jams going into the chamber (because there is another loose one under it) and when you drop the mag, the extra cartridge falls out the bottom, that is one in addition to the one which did not get into the chamber.

I am assuming this is a magazine problem, but is there a way I can be causing it?

This happens with a steel British 30 rounder.

Tnx

Double feeds, two live rounds trying to get into the chamber at once as the name implies, and separate from a failure to extract, in which a live round tries to feed into the chamber behind a fired case, are almost always magazine related.

One exception being that the piece is overfunctioning causing rounds to be dislodged from the magazine when the bolt carrier hits the end of the recoil stroke.

Use USGI mags and USGI ammo, most problems go away.