A while back on another gun board somebody mentioned some Rubbermaid nylon tool bags that Wal-Mart was selling for $7.88. I've got four of them and need more. I use one for each gun. They have two zippered sections. I use one side for the gun, the other side for mags, loader, glasses, plugs etc. The bottom section will hold four boxes(50 rd) of ammo with room to spare, you might get 6 boxes of 9mm to fit.
This way I can keep the ammo with the gun, it helps to avoid mixups. Any trip to the range usually includes a 9mm, 40 S&W, 357SIG, 32acp, and now 45acp since I bought a PT 145.
Regards, OE