On the Appleseed Qualification Test, the two rapid-fire stages require two magazines, loaded with 2 and 8 rounds respectively. To recognize which mag is which, you could mark them, but for 10/22 shooters it’s easier to shake them – the 2-round mag will make no noise, and the 8-round mag rattles. Sometimes people ask why that is…
The answer is simple:
The single round is pushed up tight against the feed lips by the long rotor vane under spring pressure.
The first round loaded (Round 1) is pushed up tightly against the second round loaded (Round 2), which is tight against the feed lips.
Beginning with the third round, Round 1 is no longer pressed against the round above – it is separated by the vanes of the magazine rotor and gravity pulls it away from the higher Round 2. There is some clearance between Round 1 and the inside of the magazine body, so that round is free to rattle a bit. The sound is faint as only one round is rattling.
As you load more rounds, the rattle gets louder because more cases are hitting the inside of the mag body as you shake it.
The photos below show an empty magazine and a full one to illustrate this explanation.
I hope this is helpful.