Magazines have always performed 100% so the rattle isn't an issue but Does anyone else have this annoyance?
This is a normal thing. The mags' internal design where it changes from double stack to single stack doesn't keep uniform pressure on all the bullets all the time. Increasing spring weight (+5% or +10%)will 'usually' minimize or eliminate the rattle if it troubles you.
Heavier springs also help prevent the second bullet in the mag from pulling forward a little when the top bullet feeds and causing a jam.
There 'was' an X-ray posted somewhere in the archives that showed the bullet stack when the mag was loaded. Would you believe the #5 witness hole does not show the 5th bullet.
I was trying to find out 'where' to drill an 11th rd witness hole. Harder to locate than it sounds--and so is the steel.