I have both the CA M24 and the M99 their mags are very similar. but not exactly..
and in comparison to the APS2 completely different.
ok here are the specs....
M24 mag
100mm long
21mm wide
42.80mm tall (BB feeding post)
M99 mag
100mm long
21.50mm wide
45.15mm tall (BB feeding post)
APS2 mag
109mm long
21.90mm wide
52.50mm tall (BB feeding post)
Now as you can see they look pretty similar but the specs show otherwise..
and the biggest problem I see in incompatibility is the width of the BB feeding post.. as seen below... the mag may fit the mag well but then not fit into the hop-up unit. As is the case with trying to use an M24 mag in the M99 with stock hop-up.
You need to be careful in finding the right ones...
but that's if you can find them at all..
Good Luck and should you find them please send me a PM so I can order spares...
hope that helps you and everyone else.