How much carry ammo is enough?

[<MADDOG>]

I think Ronin hit it on the head; "So it's impossible to tell how much carry ammo on your person is "enough".

If one wishes to carry enough ammo to to do an airfield take-down against armored aliens, and comfortable carrying such; do it. To each to his/her own. But where does the hypothetical argument end, and where does reality begin?

I must also ask: why carry the extra mag for malfunctions? I myself think one should vet the weapon, and the ammo, you are carrying for this scenario with reliability being one's first priority, and your ability to clear a bad round being second. I myself, find clearing a malfunction quicker than reloading. I may have been dropped on my head too may times though ...