how to make a weapon which can use more than one ammo?

[anala_gin]

i am from china,forgive my bad en

 

someone could tell how to realize it?

[Gorbachev]

I want this also so I can use .308 Winchester and 7.62x51mm NATO ammo in the FN FAL for personal use.

[anala_gin]

i have solved it.

 

just to declare a new ammo class,make the ammo which is exist to be son of it.