+1 on what ABTOMAT said.
"Assult Rifle" has ergonomic and layout differences, besides the simple criteria of "intermediate cartridge" and "select fire".
I would think that the term "Assult Rifle" would need ALL the following attributes:
- Intermediate rifle cartridge for both magazine capacity/weight, and balisticaly matched for close to moderate range infantry engagments.
- Detachable magazine w/capacity of 20 rounds or more.
- Select fire. Semi automatic or fully automatic. (And/or burst)
- Pistol Grip.
- In-line stock.
- Over all length no greater than 40".
- Weight less than 12 lbs/5 Kg fully loaded. (Not counting accessories)
Other rifles like the M1 Carbine, the SKS, the M14, the G3, the BAR, or the FAL all fail to meet one or more of the criteria. They are all "carbines" or "battle rifles". (Some Assult Rifles like the AR/M-16 family could also be construed as "carbines" as well, but not all "carbines", like the M1, can be considred Assult Rifles.)