Ignition/key problem

[fazersharp]

If the key is badly worn I always thought that the barrel insides are also the same -- and sort of match each other so when you get a new key cut it has nice and sharp edges and so may not work. Or is that just stupid.

I always swap my keys around from time to time so that both keys and barrel wear the same, if I didnt then if i loose a very worn key then the unused spare wont work in the worn barrel --- do yo get me ??